Electrostatic actuator and method of driving the same

ABSTRACT

An electrostatic actuator comprises first and second movable sections and a stator. The stator has a hollow frame into which the movable sections are arranged independently. Driving electrodes are provided on surfaces of the movable sections and holding electrodes are also provided on the opposite surfaces pf the movable section. A driving electrode section is provided on the inner surface of the stator facing the driving electrodes on the movable section. Also, holding electrode sections are provided on the inner surface of the stator facing the holding electrodes on the movable section. Stripes of the electrodes are arranged in a longitudinal direction and each strip is extended in a lateral direction crossing the longitudinal direction, and the holding electrodes are extended in the longitudinal direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2000-297432, filed Sep.28, 2000, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an electrostatic actuator forelectrostatically driving a slider or a movable section and a method ofdriving the same, particularly, to an electrostatic actuator includingmovable sections that can be driven individually and a method of drivingthe same.

[0004] 2. Description of the Related Art

[0005] An electrostatic actuator is small and lightweight and, thus, canbe used for the focusing of a lens system mounted to an endoscope, amovable telephone such as a portable telephone or an apparatus such asvarious kinds of PDA (Personal Digital Assistant). Such being thesituation, the electrostatic actuator attracts attentions in recentyears.

[0006]FIG. 1 is an oblique view showing the construction of aconventional electrostatic actuator 100. As shown in the drawing, theelectrostatic actuator 100 comprises a slider or movable section 101 anda stator 102. The movable section 101 is substantially in the form of aparallelepiped having a through-hole formed therein in a manner toextend in the longitudinal direction of the movable section 101, and thestator 102 is also substantially in the form of a parallelepiped havinga through-hole formed therein in a manner to extend in the longitudinaldirection of the stator 102. The movable section 101 is slidable intothe through-hole of the stator 102 such that the movable section 101 ismovable within the stator 102 in the longitudinal direction of thestator 102. Incidentally, a clearance of several microns is providedbetween the stator 102 and the movable section 101.

[0007] Also, a convex stripe electrodes 103A and 103B are formed by, forexample, an etching in the movable section 101 so as to form a pair ofelectrode surfaces facing the inner surfaces of the stator 102. Anoptical system of lenses 104 having optical axes extending along theaxis of the through-hole are fixed within the through-hole of themovable section 101. The movable section 101 is moved and the opticalsystem of these lenses is also moved with the movable section 101 so asto adjust the focus of the optical system on a subject to be examined.

[0008] A wiring 105 for applying a driving signal to the movable section101 is connected to the movable section 101. Glass plates 106A and 106Bare mounted to those inner surfaces of the stator 102 which face theelectrodes 103A and 103B, respectively, and first electrodes 107A of afirst group GA and a second group GB and second electrodes 107B of athird group GC and a fourth group GD are formed on the glass plates 106Aand 106B, respectively, by patterning a conductive material. Theelectrodes 107A of the first group GA and the second group GB arealternately arranged at the same pitch. Likewise, the electrodes 107B ofthe third group GC and the fourth group GD are also alternately arrangedin the same pitch. Also, the electrodes 107A and the electrodes 107B arearranged deviant from each other by a half pitch.

[0009] The operation of the electrostatic actuator having theconstruction described above will now be described with reference toFIG. 2.

[0010] (1) In the first step, a voltage of +V [V] is applied to thefirst group GA of the electrode 107A. As a result, an electrostaticattracting force is generated between the electrode 107A of the firstgroup GA and the electrode 103A. By this electrostatic attracting force,the movable section 101 begins to be moved toward the glass plate 106Aof the stator 102, and the electrode 103A is attracted to the electrode107A of the first group GA a predetermined time later.

[0011] (2) In the next step, a voltage of +V [V] is applied to theelectrode 107B of the third group GC among the electrodes 107B, with theresult that an electrostatic force is generated between the electrode107B of the third group GC and the electrode 103B. By this electrostaticforce, the movable section 101 begins to be moved toward the glass plate106B of the stator 102. As a result, the electrode 103B is attracted tothe electrode 107B of the third group GC a predetermined time later. Themovable section 101 is moved to the right in FIG. 2 by a distance equalto half the arranging pitch of the electrode 106A or 106B, compared withthe position described in item (1) above.

[0012] (3) Further, a voltage of +V [V] is applied to the second groupGB of the electrode 107A, with the result that an electrostatic force isgenerated between the electrode 107A of the second group GB and theelectrode 103A. By this electrostatic force, the movable section 101begins to be moved again toward the glass plate 106A, and the electrode103A is attracted to the electrode 107A of the second group GB apredetermined time later. The movable section 101 is moved to the rightin FIG. 2 by a distance equal to the arranging pitch of the electrode107A or 107B, compared with the position described in item (1) above.

[0013] (4) Still further, a voltage of +V [V] is applied to the fourthelectrode GD of the electrode 107B, with the result that anelectrostatic force is generated between the electrode 107B of thefourth group GD and the electrode 103B. By this electrostatic force, themovable section 101 begins to be moved again toward the glass substrate106B, and the electrode 103B is attracted to the electrode 107B of thefourth group GD. The movable section 101 is moved to the left in FIG. 2by a distance equal to 1.5 times as much as the arranging pitch of theelectrode 107A or 107B, compared with the position described in item (1)above.

[0014] The steps of items (1) to (4) described above are repeated so asto move the movable section 101 to the right in FIG. 2 by a distanceequal to half the arranging pitch of the electrodes every time each ofthe steps of items (2) to (4) is performed.

[0015] It should also be noted that, if the voltage is applied to theelectrode in the order of items (4), (3), (2) and (1) described above,the movable section 101 can be moved to the right in FIG. 2 by adistance equal to half the arranging pitch of the electrodes every timeeach of the steps of items (3) to (1) is performed.

[0016] It is possible to move the lens 104 mounted to the movablesection 101 by moving the movable section 101 by the steps of items (1)to (4) described above so as to adjust the focus of the lens 104 on thesubject.

[0017] As described above, in the conventional electrostatic actuator,it is possible to move the movable section to a desired position so asto adjust the focus of the lens on the subject to be photographed.However, the conventional electrostatic actuator gives rise to theproblem that it is impossible to realize the zooming function ofmagnifying or reducing the photographed image. The difficulty is basedon the mechanism that the lens system is moved with a single movablesection.

[0018] It should also be noted that, even if a plurality of movablesections are mounted to the conventional electrostatic actuator formagnifying or reducing the photographed image, it is necessary for theplural movable sections to be moved or fixed independently formagnifying or reducing the photographed image. In the electrostaticactuator of the conventional structure, however, it is impossible tooperate the electrostatic actuator with the plural movable sectionsmoved or fixed within the stator independently.

BRIEF SUMMARY OF THE INVENTION

[0019] An object of the present invention is to provide an electrostaticactuator capable of independently operating movable sections formagnifying or reducing the photographed image.

[0020] According to a first aspect of the present invention, there isprovided an electrostatic actuator, comprising:

[0021] first stator electrodes arranged in a predetermined direction andextending in a direction crossing the predetermined direction;

[0022] a second stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction;

[0023] a third stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction so as to beelectrically isolated from the second stator electrode;

[0024] a first movable section provided with first and second movablesection electrodes, arranged movable within a moving space in thepredetermined direction, the moving space being defined between thefirst stator electrodes and the second stator electrode, the firstmovable section electrodes being mounted to the first movable section toface the first stator electrodes, and the second movable sectionelectrode being mounted to the first movable section to face the secondstator electrode; and

[0025] a second movable section provided with third and fourth movablesection electrodes, arranged independently of the first movable section,the second movable section being movable within the moving space in thepredetermined direction, the third movable section electrodes beingmounted to the second movable section to face the first statorelectrodes, and the fourth movable section electrode being mounted tothe second movable section to face the third stator electrode.

[0026] According to a second aspect of the present invention, there isprovided an electrostatic actuator comprising:

[0027] a stator including a hollow stator frame having a space extendingin a predetermined direction, the stator frame having a first innersurface extending in parallel to the predetermined direction and asecond inner surface facing the first inner surface, first statorelectrodes arranged in the predetermined direction on the first innersurface and each of the stator electrode extending in a directioncrossing the predetermined direction, and second and third statorelectrodes electrically isolated each other, arranged on the secondinner surface and extending in the predetermined direction;

[0028] a first movable section arranged in the space to be movable inthe predetermined direction, the first movable section including firstmovable section electrodes facing the first stator electrodes, each ofthe first movable section electrodes extending in a direction crossingthe predetermined direction, and a second movable section electrodeextending in the predetermined direction to face the second statorelectrode;

[0029] a second movable section arranged in the space to be movable inthe predetermined direction, and including third movable sectionelectrodes facing the first electrodes, each of the third movablesection electrodes extending in a direction crossing the predetermineddirection, and a fourth movable section electrode extending in thepredetermined direction to face the third stator electrode, and

[0030] a driving circuit configured to supply a first driving signal tothe first stator electrodes, to supply one of a second driving signaland a first holding voltage signal to the second stator electrode, andto supply one of a third driving signal and a second holding voltagesignal to the third stator electrode so as to move both or one of thefirst and second movable sections in the predetermined direction.

[0031] According to a third aspect of the present invention, there isprovided an imaging apparatus for forming an image of a subject on animage-forming surface, comprising:

[0032] first stator electrodes arranged in a predetermined direction andextending in a direction crossing the predetermined direction;

[0033] a second stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction;

[0034] a third stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction so as to beelectrically isolated from the second stator electrode;

[0035] a first movable section having a first hollow space, providedwith first and second movable section electrodes, arranged movablewithin a moving space in the predetermined direction, the moving spacebeing defined between the first stator electrodes and the second statorelectrode, the first movable section electrodes being mounted to thefirst movable section to face the first stator electrodes, and thesecond movable section electrode being mounted to the first movablesection to face the second stator electrode; and

[0036] a second movable section having a second hollow space, providedwith third and fourth movable section electrodes, arranged independentlyof the first movable section, the second movable section being movablewithin the moving space in the predetermined direction, the thirdmovable section electrodes being mounted to the second movable sectionto face the first stator electrodes, and the fourth movable sectionelectrode being mounted to the second movable section to face the thirdstator electrode.

[0037] a first optical lens system having a first optical axis arrangedin the predetermined direction within the first hollow space;

[0038] a second optical system having a second optical axis arranged inthe predetermined direction within the second hollow space, the imageforming surface configured to face an image of a subject depending onthe positions of the first and second lens systems relative to theimage-forming surface; and

[0039] a driving circuit configured to supply a first driving signal tothe first stator electrodes, to supply one of a second driving signaland a first holding voltage signal to the second stator electrode, andto supply one of a third driving signal and a second holding voltagesignal to the third stator electrode so as to move both or one of thefirst and second movable sections in the predetermined direction.

[0040] According to a fourth aspect of the present invention, there isprovided a method of driving an electrostatic actuator, theelectrostatic actuator comprising:

[0041] first stator electrodes arranged in a predetermined direction andextending in a direction crossing the predetermined direction;

[0042] a second stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction;

[0043] a third stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction so as to beelectrically isolated from the second stator electrode;

[0044] a first movable section provided with first and second movablesection electrodes, arranged movable within a moving space in thepredetermined direction, the moving space being defined between thefirst stator electrodes and the second stator electrode, the firstmovable section electrodes being mounted to the first movable section toface the first stator electrodes, and the second movable sectionelectrode being mounted to the first movable section to face the secondstator electrode; and

[0045] a second movable section provided with third and fourth movablesection electrodes, arranged independently of the first movable section,the second movable section being movable within the moving space in thepredetermined direction, the third movable section electrodes beingmounted to the second movable section to face the first statorelectrodes, and the fourth movable section electrode being mounted tothe second movable section to face the third stator electrode; themethod comprising:

[0046] supplying a first driving a driving signal to the first statorelectrodes;

[0047] supplying one of a second driving voltage and a first holdingvoltage signal to the second stator electrode; and

[0048] supplying one of a third driving signal and a second holdingvoltage signal to the third stator electrode wherein both or one of thefirst and second movable sections move in the predetermined direction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0049]FIG. 1 is an oblique view schematically showing a movable sectionand a stator included in a conventional electrostatic actuator;

[0050]FIG. 2 is a vertical cross sectional view schematically showingthe construction inside the conventional electrostatic actuator;

[0051]FIG. 3A is an oblique view schematically showing the constructionof an electrostatic actuator according to a first embodiment of thepresent invention, in which pair of movable sections is located outsideof the stator frame;

[0052]FIG. 3B is an oblique view schematically showing the arrangementof the stator electrodes of the stator on the driving side shown in FIG.3A;

[0053]FIG. 3C is an oblique view schematically showing the arrangementof the stator electrodes on the side of holding the movable sectionshown in FIG. 3A;

[0054]FIG. 4A is a vertical cross sectional view schematically showingthe inner structure of the electrostatic actuator shown in FIG. 3A;

[0055]FIG. 4B is a cross sectional view schematically showing theconstruction of the electrostatic actuator along the line X-X shown inFIG. 4A;

[0056]FIG. 4C is a cross sectional view schematically showing theconstruction of the electrostatic actuator along the line Y-Y shown inFIG. 4A;

[0057]FIG. 4D is a cross sectional view schematically showing therelationship between the number of holding electrodes and the sidesurface gap in the electrostatic actuator shown in FIG. 4A;

[0058]FIGS. 5A to 5F are timing charts showing the voltages applied tothe electrodes of the stator in the case where two movable sections aresimultaneously moved in the same direction in the electrostatic actuatorshown in FIG. 4A;

[0059]FIGS. 6A to 6F are timing charts showing the voltages applied tothe electrodes of the stator in the case where one of two movablesections is moved in a certain direction in the electrostatic actuatorshown in FIG. 4A;

[0060]FIGS. 7A to 7F are timing charts showing the voltages applied tothe electrodes of the stator in the case where the other of the twomovable sections is moved in a certain direction in the electrostaticactuator shown in FIG. 4A;

[0061]FIGS. 8A to 8C are cross sectional views directed to amodification of the electrostatic actuator shown in FIG. 4A and eachshowing schematically the operating states of two movable sections;

[0062]FIGS. 9A to 9F are timing charts showing the voltages applied tothe electrodes of the stator in the case where two movable sections aresimultaneously moved in the same direction in the electrostatic actuatorshown in FIG. 8A;

[0063]FIGS. 10A to 10F are timing charts showing the voltages applied tothe electrodes of the stator in the case where one of two movablesections is moved in a certain direction in the electrostatic actuatorshown in FIG. 8B;

[0064]FIGS. 11A to 11F are timing charts showing the voltages applied tothe electrodes of the stator in the case where the other of the twomovable sections is moved in a certain direction in the electrostaticactuator shown in FIG. 8C;

[0065]FIG. 12A is a vertical cross sectional view schematically showingthe inner structure of an electrostatic actuator according to amodification of the first embodiment of the present invention;

[0066]FIG. 12B is a graph showing the relationship between the positionsof the first and second movable sections and the optical magnificationin the electrostatic actuator shown in FIG. 12A;

[0067]FIG. 13A is a vertical cross sectional view schematically showingthe movable section of an electrostatic actuator according to amodification of a second embodiment of the present invention;

[0068]FIG. 13B is a plan view schematically showing the electrodepattern on the lower surface of the movable section shown in FIG. 13A;

[0069]FIG. 13C is a plan view schematically showing the electrodepattern on the glass plate of a stator of the electrostatic actuatorhaving the movable sections shown in FIGS. 13A and 13B incorporatedtherein;

[0070]FIG. 14A is a vertical cross sectional view schematically showingthe movable section of the electrostatic actuator according to amodification of the second embodiment of the present invention;

[0071]FIG. 14B is a plan view schematically showing the electrodepattern on the lower surface of the movable section shown in FIG. 14A;

[0072]FIG. 14C is a plan view schematically showing the electrodepattern on the glass plate of the stator of an electrostatic actuatorhaving the movable sections shown in FIGS. 14A and 14B incorporatedtherein;

[0073]FIG. 15A is plan view schematically showing in a dismantled statethe movable section of the electrostatic actuator shown in FIG. 4A;

[0074]FIG. 15B is an oblique view schematically showing the assembledstate of the movable section shown in FIG. 15A;

[0075]FIG. 15C is a cross sectional view schematically showing themovable section shown in FIG. 15B and a mold having the movable sectionincorporated therein;

[0076]FIG. 15D is an oblique view schematically showing the movablesection prepared by using the mold shown in FIG. 15C;

[0077]FIG. 16A is an oblique view schematically showing in a partlyperspective fashion the mold for manufacturing the stator of theelectrostatic actuator shown in FIG. 4A;

[0078]FIG. 16B is an oblique view schematically showing a glass plateused for manufacturing the stator included in the electrostatic actuatorshown in FIG. 4A;

[0079]FIG. 16C is an oblique view schematically showing in a partlyperspective fashion the assembled structure by mounting a glass plate tothe mold of the stator shown in FIG. 16A;

[0080]FIG. 16D is an oblique view schematically showing the core mountedto the mold of the stator shown in FIG. 16C;

[0081]FIG. 17A is an oblique view schematically showing the electrode ofthe movable section used in the method of manufacturing theelectrostatic actuator of the present invention;

[0082]FIG. 17B is an oblique view schematically showing the body of themovable section used in the method of manufacturing the electrostaticactuator of the present invention;

[0083]FIG. 17C is an oblique view schematically showing the movablesection prepared by fixing the electrode of the movable section shown inFIG. 17A to the body of the movable section shown in FIG. 17B;

[0084]FIG. 18 is a vertical cross sectional view schematically showingthe movable section used in the manufacturing method of an electrostaticactuator of the present invention and a mold of the movable section; and

[0085]FIG. 19 is a plan view schematically showing a mold of the movablesection and the stator used in the manufacturing method of anelectrostatic actuator of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0086] Electrostatic actuators according to some embodiments of thepresent invention will now be described with reference to theaccompanying drawings.

[0087] The electrostatic actuator, which is small and lightweight, canbe used for the focusing of the lens mounted to an endoscope, a movabletelephone such as a portable telephone and various PDA's (PersonalDigital Assistants) and, thus, attracts attentions in recent years.

[0088]FIGS. 3A to 4A collectively show an electrostatic actuatoraccording to a first embodiment of the present invention.

[0089]FIG. 3A is an oblique view schematically showing the electrostaticactuator 1 according to the first embodiment of the present invention.The electrostatic actuator 1 shown in FIG. 3A comprises first and secondmovable sections 2A and 2B having a pair of movable section electrodes4, 8 and another pair of movable section electrodes 5, 11 formed on theupper surfaces and the lower surfaces, respectively, and a stator 3having a pair of stator electrode sections 12, 14 arranged to face themovable section electrodes 4, 8 on the upper surfaces and the movablesection electrodes 5, 11 on the lower surfaces of the movable sections2A, 2B, respectively.

[0090] The movable section electrodes 4, 8, 5, 11 are grouped intodriving electrodes 4, 8 for driving the movable sections 2A, 2B and theholding electrodes 5, 11 for fixing the movable sections 2A, 2B. On theother hand, the stator electrode sections 12, 14 are grouped into adriving electrode 12 for driving the stator and a holding electrode 14for holding the movable sections 2A, 2B at the desired positions.

[0091] The construction of the stator 3 will now be described.Specifically, the stator 3 is formed of a stator frame 3A formed of aframe of a hollow cube having a through-hole formed therein. The statorframe 3A has an upper inner surface 3A-1, a lower inner surface 3A-2,and side inner surfaces 3A-3 and 3A-4.

[0092] A driving electrode section 12 for driving the movable sections2A, 2B is formed on one inner surface of the stator frame 3A, e.g., onthe upper inner surface 3A-1. Further, a holding electrode section 14for holding the movable sections 2A, 2B at the desired positions isformed on another inner surface facing the upper inner surface of thestator frame 3A, e.g., on the lower inner surface 3A-2.

[0093] The driving electrode section 12 is patterned in a desired shapeand formed on the surface of a glass plate 13 in a manner to form aplurality of electrode stripes extending in, for example, the directionperpendicular to the longitudinal direction of the stator 3, i.e.,extending in the lateral direction of the stator 3, as shown in FIG. 3A.Incidentally, the glass plate 13 having the driving electrode section 12formed thereon is fitted to the inner surface 3A-1 of the stator 3.Also, each of the electrode stripes 12A to 12D of the driving electrodesection 12 has a width of about 20 μm. Also, the clearance between theadjacent electrode stripes of the electrode stripes 12A to 12D of thedriving electrode section 12 is about 20 μm, and the electrode stripes12A to 12D are arranged at a pitch of about 40 μm.

[0094] A holding electrode section 14 is formed on the inner surface3A-2 of the stator frame 3A facing the driving electrode section 12. Theholding electrode section 14 is patterned in a desired shape and formedin a predetermined direction on the surface of a glass plate 15. Theglass plate 15 having the holding electrode formed thereon is fitted tothe inner surface 3A-2 of the stator 3. It should be noted that 5electrode stripes are formed in parallel in the holding electrodesection 14 in a manner to correspond to 3 holding electrodes 5 on theside of the movable section of a first movable section 2A referred toherein later and 2 holding electrodes 11 on the side of the movablesection of a second movable section 2B referred to herein later. The 5holding electrode section 14 shown in FIG. 3A are arranged apart fromeach other in substantially the entire region including the centralregion on the glass substrate 15. The holding electrode sections 14Acorresponding to the fixing electrode 5 on the side of the movablesection are electrically connected at the edge portion of the glassplate 15 in one of the side regions in the longitudinal direction of theglass plate 15, and the 2 holding electrode sections 14B correspondingto the fixing electrode 11 on the side of the movable section areelectrically connected in the other side regions in the longitudinaldirection on the glass plate 15. What should be noted is that theholding electrode sections 14A and 14B are arranged electricallyindependently so as to control independently the first and secondmovable sections 2A, 2B.

[0095] Stoppers 16 are formed on the side inner surfaces 3A-3, 3A-4 ofthe stator frame 3A for preventing the side surfaces of the first andsecond movable sections 2A, 2B from contacting directly the side innersurfaces 3A-3, 3A-4. Similarly, stoppers (not shown) are formed on theinner surfaces 3A-1, 3A-2 for preventing the movable sections 2A, 2Bfrom being brought into direct contact with the driving electrodes 12,14.

[0096] The construction of each of the two movable sections 2A, 2B willnow be described in detail.

[0097] Specifically, the first movable section 2A comprises asubstantially parallelepiped hollow support body formed of an electricconductive member, the electrodes 4, 5 formed on the outer surfaces ofthe hollow support body, a lens 6 arranged in the hollow portion of thesupport body, and a wiring 7 for removing the electric charge from thesupport body. Likewise, the second movable section 2B comprises asubstantially parallelepiped hollow support body formed of an electricconductive member, the electrodes 8, 11 formed on the outer surfaces ofthe hollow support body, a lens 9 arranged in the hollow portion of thesupport body, and a wiring 10 for removing the electric charge from thesupport body. The support body and electrodes 4, 5 may be formed into aunitary configuration.

[0098] The first movable section 2A and the second movable section 2Bare inserted apart from each other into the through-hole of the supportbody such that these first and second movable sections 2A and 2B aremovable in a predetermined direction.

[0099] A driving electrode 4 on the side of the movable section isformed on a surface of the first movable section 2A facing the drivingelectrode section 12 on the side of the stator, e.g., on the uppersurface of the first movable section 2A. Likewise, a fixing electrode 5on the side of the movable section is formed on a surface of the firstmovable section 2A facing the holding electrode section 14, e.g., on thelower surface of the first movable electrode 2A. The driving electrode 4on the side of the movable section is formed by etching in the form of aplurality of projecting stripes extending in a direction perpendicularto the moving direction and arranged in the longitudinal direction.Also, the fixing electrode 5 on the side of the movable section isformed by etching in the form of a plurality of projecting stripesextending in the moving direction and arranged in the lateral direction.The driving electrode 4 on the side of the movable section is formed tocomprise concave portions and convex portions with a clearance of about20 μm provided between the adjacent concave and convex portions. Theheight of the convex portion from the surface inside the concave portionis about 10 μm. In other words, the edge surface of the convex portionof the driving electrode 4 on the side of the movable section has awidth equal to the width of one of the electrodes 12A to 12D of thedriving electrode section 12. Also, the bottom surface of the concaveportion of the driving electrode 4 on the side of the movable sectionhas a width equal to the clearance between the adjacent electrodes 12Ato 12D. The concave or convex portions of the driving electrode 4 on theside of the movable section 4 arranged at a pitch of about 40 μm.

[0100] In the actuator shown in FIG. 3A, three holding electrodes 5extending in the longitudinal direction and arranged in the lateraldirection are mounted to the first movable section 2A. Also, a pluralityof lenses 6 having aligned optical axes are fixed within thethrough-hole of the first movable section 2A.

[0101] A driving electrode 8 on the side of the movable section having ashape and a dimension equal to those of the driving electrode 4 on theside of the movable section of the first movable section 2A is mountedto the second movable section 2B. Also, a lens 9 similar to the lens 6is fixed within the through-hole of the second movable section 2B. Thelens system formed by the lenses 6 and 9 is zoomed between thewide-angle and telephoto lens systems by changing the arrangement of thelenses 6 and 9 so as to adjust the focus on the subject in accordancewith the zoomed focal length. Two holding electrodes 11 extending in thelongitudinal direction and arranged in the lateral direction are mountedto the second movable section 2B. The holding electrodes 11 are formedby etching.

[0102] As apparent from the above description, the driving electrodes 4,8 on the side of the movable section are formed such that the concaveand convex portions of these driving electrodes 4, 8 are substantiallyparallel to each other. The holding electrodes 5, 11 on the side of themovable section are also formed such that the concave and convexportions thereof are substantially parallel to each other. The extendingdirections of the driving electrodes 4, 8 on the side of the movablesection are allowed to cross the extending directions of the holdingelectrodes 5, 11 on the side of the movable section. Also, the holdingelectrodes 5, 11 on the side of the movable section extend in thelongitudinal direction and are arranged in parallel such that theseholding electrodes 5, 11 do not overlap with other in the lateraldirection.

[0103] The first and second movable sections 2A, 2B are arranged in themoving direction, i.e., in the longitudinal direction, and areindependently movable in the longitudinal direction.

[0104] The operation of the actuator of the particular construction willnow be described with reference to FIGS. 4A to 4D. FIG. 4A is a crosssectional view showing the state that the first and second movablesections 2A, 2B are inserted into the through-hole of the stator frame3A. FIG. 4B is a lateral cross sectional view along the lines X-X asviewed in the direction denoted by an arrow. Further, FIG. 4C is alateral cross sectional view along the line Y-Y as viewed in thedirection denoted by an arrow.

[0105] The driving electrode section 12 is formed of a plurality ofelectrode groups each consisting of electrodes 12A to 12D of 4 phasesarranged in the moving direction, as shown in FIG. 4A. These drivingelectrodes 12A to 12D are connected to a control unit 19 so as to bedriven upon receipt of control voltage signals from the control unit 19.To be more specific, the groups of the driving electrodes 12A to 12D aresequentially arranged in the longitudinal direction, and each of thedriving electrodes 12A to 12D are commonly connected to thecorresponding driving electrode and connected to the control unit 19,and a voltage signal is applied independently to the driving electrodestripes 12A to 12D of each group. For example, where voltage is appliedto the driving electrode 12A, a voltage signal is applied to the convexportion corresponding to the driving electrode 12A of all the groups ofthe electrode section 12.

[0106] As shown in FIG. 4D, it is necessary for the width Wm of thefixing electrode 5 or 11 of the movable section 2A or 2B and the widthWs of the fixing electrode 14 of the stator 3 to be set larger than theallowable moving length ΔL even if the movable section 2A or 2B is movedin the lateral direction within the frame of the stator 3. The allowablemoving length ΔL corresponds to a difference between the distance Lsbetween the stoppers, and the width Lm of the movable section 2A or 2B.The allowable moving length ΔL is produced in the actuator when themovable section 2A or 2B abuts against a stopper 16 mounted to the sidesurface of one of the stator 5 or 11 and the stopper mounted to one sidesurface of the stator 5 or 11. In the present invention, each of Wm andWs is set larger than the allowable moving length ΔL. Difficulties aregenerated if this requirement is not satisfied. Specifically, if themovable section is moved sideward by the moving length ΔL, the mutuallyfacing electrodes 5 and 14 are deviated from each other. Also, if theoverlapping area is made extremely small, the force to fix the movablesection 2A ceases to be generated.

[0107] Also, the free space between adjacent electrodes 5, adjacentelectrodes 11 or adjacent electrodes 14 must be greater than the movinglength ΔL. If the number of holding electrodes is increased, the portionwhere the electrode is not mounted is also increased. This is adisadvantageous condition for generating an attractive force.

[0108] It should also be noted that, if the movable sections 2A, 2B havea single electrode 5 and a single electrode 11 respectively, the singleelectrodes can not be symmetrically arranged in respect to a movingdirection of the movable section 2A, 2B so that the movable sections 2A,2B tend to be moved unstable in the driving step. It follows that it isnecessary to mount at least two electrodes to each of the movablesections 2A and 2B.

[0109] Such being the situation, in a small actuator having, forexample, two systems of stator electrodes as the holding electrodes, itis desirable to employ a combination that two electrodes are mounted toone of the movable sections 2A, 2B and three electrodes are mounted tothe other of the movable sections 2A, 2B or another combination thatthree electrodes are mounted to one of the movable sections 2A, 2B andfour electrodes are mounted to the other of the two movable sections 2A,2B.

[0110] There are four operation modes in the first and second movablesections 2A, 2B. Each of these operation modes will now be described.

[0111] (I) Where each of the first and second movable sections 2A and 2Bis moved to the right in FIG. 4A (hereinafter referred to as mode I):

[0112] This operation corresponds to the focusing mode in which thefocus of the lens system is aligned on the subject.

[0113] (II) Where each of the first and second movable sections 2A and2B is moved to the right in FIG. 4A (hereinafter referred to as modeII):

[0114] This operation also corresponds to the focusing mode in which thefocus of the lens system is aligned on the subject.

[0115] (III) Where the first movable section 2A is held stationary andthe second movable section 2B alone is moved to the left or to the rightin FIG. 4A (hereinafter referred to as operation mode III):

[0116] This operation corresponds to the zooming mode in which the lenssystem is switched to the telephoto side or the wide-angle side.

[0117] (IV) Where the second movable section 2A is held stationary andthe first movable section 2B alone is moved to the left or to the rightin FIG. 4A (hereinafter referred to as operation mode IV):

[0118] This operation corresponds to the zooming mode in which the lenssystem is switched to the telephoto side or the wide-angle side.

[0119] The four operation modes summarized above will now be describedin detail.

[0120] (I) Operation mode I in which the first and second movablesections 2A and 2B are moved to the right in FIG. 4A is performed asfollows:

[0121] (1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are kept connected to the ground. Under this condition,a voltage H is applied to the driving electrodes 12A as shown in FIG.5A. As a result, the driving electrodes 4, 8 on the side of the movablesection in the vicinity of the driving electrode 12A are attracted bythe electrostatic force toward the driving electrode 12A, with theresult that the driving electrodes 4, 8 on the side of the movablesection are attracted to the driving electrode 12A. It follows that thefirst and second movable sections 2A, 2B are moved toward the glassplate 13.

[0122] (2) In the next step, the voltage of the driving electrode 12A ischanged into a low level L at time t1, and a voltage H is applied to theholding electrode sections 14A, 14B as shown in FIGS. 5E and 5F. As aresult, a strong electrostatic force is generated between the holdingelectrode section 14A and the fixing electrode 5 on the side of themovable section so as to permit the first movable section 2A to be movedtoward the glass plate 15. It follows that the fixing electrode 5 on theside of the movable section is attracted to the holding electrodesection 14A. Also, a strong electrostatic force is generated between theholding electrode section 14B and the fixing electrode 11 on the side ofthe movable section. As a result, the second movable section 2B is movedtoward the glass plate 15 so as to permit the fixing electrode 11 on theside of the movable section to be attracted to the holding electrodesection 14B.

[0123] (3) In the next step, voltage of the holding electrode sections14A, 14B is changed into a low level L at time t2, with the result thata voltage H is applied to the driving electrode 12B as shown in FIG. 5B.As a result, the driving electrodes 4, 8 on the side of the movablesection in the vicinity of the driving electrode 12B is attracted by anelectrostatic force toward the driving electrode 12B, with the resultthat the driving electrodes 4, 8 on the side of the movable section areattracted to the driving electrode 12B. It follows that the first andsecond movable electrodes 2A, 2B are moved toward the glass plate 13. Inthis step, the first and second movable sections 2A, 2B are moved to theright in FIG. 4A by a distance equal to one stripe of the drivingelectrode section 12, i.e., a distance equal to one pitch, compared withthe position described in item (1) above.

[0124] (4) In the next step, voltage of the driving electrode 12B ischanged to a low level L at time t3, with the result that a voltage H isapplied again to the holding electrode sections 14A, 14B, as shown inFIGS. 5E and 5F, so as to generate a strong electrostatic force betweenthe holding electrode section 14A and the fixing electrode 5 on the sideof the movable section. It follows that the first movable section 2A ismoved toward the glass plate 15 and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section is attracted to the holding electrode section 14B.

[0125] (5) Further, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t4, with the result that avoltage is applied to the driving electrode 12C, as shown in FIG. 5C. Inthis case, the driving electrodes 4, 8 on the side of the movablesection in the vicinity of the driving electrode 12C are attracted by anelectrostatic force toward the driving electrode 12C such that thedriving electrodes 4, 8 on the side of the movable section are attractedto the driving electrode 12C. As a result, the first and second movablesections 2A, 2B are moved toward the glass plate 13. In this case, thefirst and second movable sections 2A, 2B are moved to the right in FIG.4A by a distance equal to two stripes of the driving electrode section12, i.e., a distance equal to two pitches, compared with the positiondescribed in item (1) above.

[0126] (6) In the next step, voltage of the driving electrode 12C ischanged to a low level L at time t5, with the result that a voltage isapplied again to the holding electrode sections 14A, 14B, as shown inFIGS. 5E and 5F, so as to generate a strong electrostatic force betweenthe holding electrode section 14A and the fixing electrode 5 on the sideof the movable section. It follows that the first movable section 2A ismoved toward the glass plate 15 and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section is attracted to the holding electrode section 14B.

[0127] (7) In the next step, the voltage of the holding electrodesections 14A, 14B is changed into a low level L at time t6, with theresult that a voltage is applied to the driving electrode 12D, as shownin FIG. 5D. In this case, the driving electrodes 4, 8 on the side of themovable section in the vicinity of the driving electrode 12D areattracted by an electrostatic force toward the driving electrode 12Dsuch that the driving electrodes 4, 8 on the side of the movable sectionare attracted to the driving electrode 12D. As a result, the first andsecond movable sections 2A, 2B are moved toward the glass plate 13. Inthis case, the first and second movable sections 2A, 2B are moved to theright in FIG. 4A by a distance equal to three stripes of the drivingelectrode section 12, i.e., a distance equal to three pitches, comparedwith the position described in item (1) above.

[0128] (8) In the next step, voltage of the driving electrode 12D ischanged to a low level L at time t7, with the result that a voltage isapplied again to the holding electrode sections 14A, 14B, as shown inFIGS. 5E and 5F, so as to generate a strong electrostatic force betweenthe holding electrode section 14A and the fixing electrode 5 on the sideof the movable section. It follows that the first movable section 2A ismoved toward the glass plate 15 and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14A. Also, a strong electrostatic force is generated between the holdingelectrode section 14B and the fixing electrode 11 on the side of themovable section. As a result, the second movable section 2B is movedtoward the glass plate 15, and the fixing electrode 11 on the side ofthe movable section is attracted to the holding electrode section 14B.

[0129] (9) Further, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t8, with the result that avoltage is applied to the driving electrode section 12A, as shown inFIG. 5A. In this case, the driving electrodes 4, 8 on the side of themovable section in the vicinity of the driving electrode section 12A areattracted by an electrostatic force toward the driving electrode section12A such that the driving electrodes 4, 8 on the side of the movablesection are attracted to the driving electrode 12C. As a result, thefirst and second movable sections 2A, 2B are moved toward the glassplate 13. In this case, the first and second movable sections 2A, 2B aremoved to the right in FIG. 4A by a distance equal to four stripes of thedriving electrode section 12, i.e., a distance equal to four pitches,compared with the position described in item (1) above.

[0130] The steps of items (1) to (9) described above are repeated untilthe first and second movable sections 2A, 2B are moved by a desireddistance.

[0131] (II) Operation mode II in which the first and second movablesections 2A, 2B are both moved to the left in FIG. 4A will now bedescribed.

[0132] The first and second movable sections 2A, 2B can be moved to theright in FIG. 4A if the steps for operation mode I described above arecarried out in the opposite direction. To be more specific, the firstand second movable sections 2A, 2B can be moved to the right in FIG. 4Aby repeating the steps for operation mode I in the order of steps (9),(8), (7), (6), (5), (4), (3), (2) and (1). Of course, the number ofrepetitions is determined in accordance with the desired distance ofmovement of the first and second movable sections 2A, 2B.

[0133] It should be noted that each of operation modes I and II is anoperation of the focusing mode for aligning the focus on the subject.Whether to employ operation mode I or II is determined appropriatelydepending on the initial positions of the first and second movablesections 2A, 2B and on the direction of the movement of the first andsecond movable sections 2A, 2B which permits achieving the focusing in ashorter time.

[0134] (III) Operation mode III in which the first movable section 2A isheld stationary and the second movable section 2B alone is moved to theleft or to the right in FIG. 4A will now be described.

[0135] Let us describe first the case where the second movable section2B is moved to the right in FIG. 4A.

[0136] (1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are kept connected to the ground as in operation mode Idescribed previously. Then, a voltage is applied to the holdingelectrode section 14B as shown in FIG. 6F. As a result, an electrostaticforce is generated between the holding electrode section 14B and thefixing electrode 5 on the side of the movable section. It follows thatthe second movable section 2B is moved toward the glass plate 15, andthe fixing electrode 5 on the side of the movable section is attractedto the holding electrode section 14B. Where voltage is applied to theholding electrode section 14A as shown in FIG. 6E, the first movablesection 2A is attracted to and fixed temporarily to the glass plate 15.

[0137] (2) In the next step, a voltage H is applied to the drivingelectrode 12A at time t1 as shown in FIG. 6A, with the voltage H keptapplied to the holding electrode section 14A as shown in FIG. 6E. As aresult, the driving electrode 8 on the side of the movable section 2B inthe vicinity of the driving electrode 12A is attracted by anelectrostatic force, with the result that the driving electrode 8 on theside of the movable section 2B is attracted to the driving electrode12A. It follows that the second movable section 2B is moved toward theglass plate 13. On the other hand, since the voltage H is kept appliedto the holding electrode section 14A, the first movable section 2A iskept fixed on the side of the glass plate 15.

[0138] (3) In the next step, a voltage H is applied to the holdingelectrode section 14B at time t2 as shown in FIG. 6F, with voltage keptapplied to the holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section. As aresult, the second movable section 2B is moved toward the glass plate15, and the fixing electrode 11 on the side of the movable section 2B isattracted to the holding electrode section 14B.

[0139] (4) In the next step, a voltage H is applied to the drivingelectrode 12B at time t3 as shown in FIG. 6B with the voltage keptapplied to the holding electrode section 14A. As a result, the drivingelectrode 8 on the side of the movable section 2B in the vicinity of thedriving electrode 12B is attracted toward the driving electrode 12B byan electrostatic force, and the driving electrode 8 on the side of themovable section 2B is attracted to the driving electrode 12B. It followsthat the second movable section 2B is moved toward the glass plate 13.On the other hand, the first movable section 2A is similarly kept fixedon the side of the glass plate 15. In this case, the second movablesection 2B is moved to the right in FIG. 4A by a distance equal to onestripe of the driving electrode section 12, i.e., a distance equal toone pitch, compared with the position described in item (1) above.

[0140] (5) In the next step, a voltage H is applied to the holdingelectrode section 14B at time t4 as shown in FIG. 6F, with voltage keptapplied to the holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section 2B.As a result, the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable sectionis attracted to the holding electrode section 14B.

[0141] (6) In the next step, a voltage is applied to the drivingelectrode 12C at time t5 as shown in FIG. 6C with the voltage keptapplied to the holding electrode section 14A. As a result, the drivingelectrode 8 on the side of the movable section 2B in the vicinity of thedriving electrode 12C is attracted toward the driving electrode 12C byan electrostatic force, and the driving electrode 8 on the side of themovable section is attracted to the driving electrode 12C. It followsthat the second movable section 2B is moved toward the glass plate 13.On the other hand, the first movable section 2A is similarly kept fixedon the side of the glass plate 15. In this case, the second movablesection 2B is moved to the right in FIG. 4A by a distance equal to twostripes of the driving electrode section 12, i.e., a distance equal totwo pitches, compared with the position described in item (1) above.

[0142] (7) In the next step, a voltage H is applied to the holdingelectrode section 14B at time t6 as shown in FIG. 6F, with voltage keptapplied to the holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section 2B.As a result, the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable section2B is attracted to the holding electrode section 14B.

[0143] (8) In the next step, a voltage is applied to the drivingelectrode stripe 12D at time t7 as shown in FIG. 6D with the voltagekept applied to the holding electrode section 14A. As a result, thedriving electrode 8 on the side of the movable section 2B in thevicinity of the driving electrode stripe 12D is attracted toward thedriving electrode section 12D by an electrostatic force, and the drivingelectrode 8 on the side of the movable section 2B is attracted to thedriving electrode section 12D. It follows that the second movablesection 2B is moved toward the glass plate 13. On the other hand, thefirst movable section 2A is similarly kept fixed on the side of theglass plate 15. In this case, the second movable section 2B is moved tothe right in FIG. 4A by a distance equal to three stripes of the drivingelectrode section 12, i.e., a distance equal to three pitches, comparedwith the position described in item (1) above.

[0144] (9) In the next step, a voltage is applied to the holdingelectrode section 14B at time t8 as shown in FIG. 6F, with voltage keptapplied to the holding electrode section 14A. It follows that a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section. As aresult, the second movable section 2B is moved toward the glass plate15, and the fixing electrode 11 on the side of the movable section isattracted to the holding electrode section 14B.

[0145] (10) In the next step, a voltage is applied to the drivingelectrode 12A at time t9 as shown in FIG. 6A with the voltage keptapplied to the holding electrode section 14A. As a result, the drivingelectrode 8 on the side of the movable section in the vicinity of thedriving electrode 12A is attracted toward the driving electrode section12A by an electrostatic force, and the driving electrode 8 on the sideof the movable section is attracted to the driving electrode 12A. Itfollows that the second movable section 2B is moved toward the glassplate 13. On the other hand, the first movable section 2A is similarlykept fixed on the side of the glass plate 15. In this case, the secondmovable section 2B is moved to the right in FIG. 4A by a distance equalto four stripes of the driving electrode section 12, i.e., a distanceequal to four pitches, compared with the position described in item (1)above.

[0146] The steps of items (1) to (10) described above are repeated untilthe second movable section 2B is moved by a desired distance.

[0147] Also, where it is intended to move the second movable section 2Bto the right in FIG. 4A, the steps of items (1), (10), (9), (8), (7),(6), (5), (4), (3) and (2) in the operation mode III described above arerepeated in the order mentioned so as to move the second movable section2B by a desired distance.

[0148] (IV) Operation mode IV in which the second movable section 2B isheld stationary and the first movable section 2A alone is moved to theleft or to the right in FIG. 4A will now be described.

[0149] Let us describe first the case where the first movable section 2Ais moved to the right in FIG. 4A.

[0150] (1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are kept connected to the ground as in operation mode Idescribed previously. Then, a voltage H is applied to the holdingelectrode section 14A as shown in FIG. 7E. As a result, an electrostaticforce is generated between the holding electrode section 14A and thefixing electrode 11 on the side of the movable section. It follows thatthe first movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section 2A is attracted tothe holding electrode section 14A. Where voltage is applied to theholding electrode section 14B as shown in FIG. 7F, the second movablesection 2B is attracted to and fixed to the glass plate 15.

[0151] (2) In the next step, a voltage H is applied to the drivingelectrode 12A at time t1 as shown in FIG. 7A, with the voltage H keptapplied to the holding electrode section 14B as shown in FIG. 7F. As aresult, the driving electrode 4 on the side of the movable section 2A inthe vicinity of the driving electrode 12A is attracted by anelectrostatic force to the driving electrode 12A, with the result thatthe driving electrode 4 on the side of the movable section 2A isattracted to the driving electrode 12A. It follows that the firstmovable section 2A is moved toward the glass plate 13. On the otherhand, since the voltage H is kept applied to the holding electrodesection 14B, the second movable section 2B is kept fixed on the side ofthe glass plate 15.

[0152] (3) In the next step, a voltage H is applied to the holdingelectrode section 14A at time t2 as shown in FIG. 7F, with voltage keptapplied to the holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section 2A. Asa result, the first movable section 2A is moved toward the glass plate15, and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

[0153] (4) In the next step, a voltage H is applied to the drivingelectrode 12B at time t3 as shown in FIG. 7B with the voltage keptapplied to the holding electrode section 14B. As a result, the drivingelectrode 4 on the side of the movable section 2A in the vicinity of thedriving electrode 12B is attracted toward the driving electrode 12B byan electrostatic force, and the driving electrode 4 on the side of themovable section 2A is attracted to the driving electrode 12B. It followsthat the first movable section 2A is moved toward the glass plate 13. Onthe other hand, the second movable section 2B is similarly kept fixed onthe side of the glass plate 15. In this case, the first movable section2A is moved to the right in FIG. 4A by a distance equal to one stripe ofthe driving electrode section 12, i.e., a distance equal to one pitch,compared with the position described in item (1) above.

[0154] (5) In the next step, a voltage H is applied to the holdingelectrode section 14A at time t4 as shown in FIG. 7E, with voltage keptapplied to the holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section 2A. Asa result, the first movable section 2A is moved toward the glass plate15, and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

[0155] (6) In the next step, a voltage H is applied to the drivingelectrode 12C at time t5 as shown in FIG. 7C with the voltage keptapplied to the holding electrode section 14B. As a result, the drivingelectrode 4 on the side of the movable section 2A in the vicinity of thedriving electrode 12C is attracted toward the driving electrode 12C byan electrostatic force, and the driving electrode 4 on the side of themovable section 2A is attracted to the driving electrode 12C. It followsthat the first movable section 2A is moved toward the glass plate 13. Onthe other hand, the second movable section 2B is similarly kept fixed onthe side of the glass plate 15. In this case, the first movable section2A is moved to the right in FIG. 4A by a distance equal to two stripesof the driving electrode section 12, i.e., a distance equal to twopitches, compared with the position described in item (1) above.

[0156] (7) In the next step, a voltage H is applied to the holdingelectrode section 14A at time t6 as shown in FIG. 7E, with voltage keptapplied to the holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section 2A. Asa result, the first movable section 2A is moved toward the glass plate15, and the fixing electrode 5 on the side of the movable section isattracted to the holding electrode section 14A.

[0157] (8) In the next step, a voltage H is applied to the drivingelectrode stripe 12D at time t7 as shown in FIG. 7D with the voltagekept applied to the holding electrode section 14B. As a result, thedriving electrode 4 on the side of the movable section 2A in thevicinity of the driving electrode stripe 12D is attracted toward thedriving electrode section 12D by an electrostatic force, and the drivingelectrode 4 on the side of the movable section 2A is attracted to thedriving electrode section 12D. It follows that the first movable section2A is moved toward the glass plate 13. On the other hand, the secondmovable section 2B is similarly kept fixed temporarily on the side ofthe glass plate 15. In this case, the first movable section 2A is movedto the right in FIG. 4A by a distance equal to three stripes of thedriving electrode section 12, i.e., a distance equal to three pitches,compared with the position described in item (1) above.

[0158] (9) In the next step, a voltage H is applied to the holdingelectrode section 14A at time t8 as shown in FIG. 7E, with voltage keptapplied to the holding electrode section 14B. It follows that a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section. As aresult, the first movable section 2A is moved toward the glass plate 15,and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

[0159] (10) In the next step, a voltage H is applied to the drivingelectrode 12A at time t9 as shown in FIG. 7A with the voltage keptapplied to the holding electrode section 14B. As a result, the drivingelectrode 4 on the side of the movable section 2A in the vicinity of thedriving electrode 12A is attracted toward the driving electrode section12A by an electrostatic force, and the driving electrode 4 on the sideof the movable section 2A is attracted to the driving electrode 12A. Itfollows that the first movable section 2A is moved toward the glassplate 13. On the other hand, the second movable section 2B istemporarily kept fixed on the side of the glass plate 15. In this case,the first movable section 2A is moved to the left in FIG. 4A by adistance equal to four stripes of the driving electrode section 12,i.e., a distance equal to four pitches, compared with the positiondescribed in item (1) above.

[0160] The steps of items (1) to (10) described above are repeated untilthe first movable section 2A is moved by a desired distance.

[0161] Also, where it is intended to move the first movable section 2Ato the left in FIG. 4A, the steps of items (1), (10), (9), (8), (7),(6), (5), (4), (3) and (2) in the operation mode III described above arerepeated in the order mentioned so as to move the first movable section2A by a desired distance.

[0162] It should be noted that each of operation modes III and VI is anoperation for magnifying or reducing the photographed image. Whether toemploy operation mode III or IV is determined appropriately depending onthe initial positions of the first and second movable sections 2A, 2Band on the direction of the movement of the first and second movablesections 2A, 2B which permits achieving the magnification or reductionin a shorter time.

[0163] Incidentally, FIG. 4B shows that the first movable section 4B ismoved toward the glass plate 13, and FIG. 4C shows that the secondmovable section 2B is moved toward the glass plate 15.

[0164] In the actuator shown in FIG. 4A, each of the driving electrodes12A to 12D of the driving electrode section 12 is set substantiallyequal to the width of each of the driving electrodes 4 and 8 on the sideof the movable section and the arranging pitch of these drivingelectrodes 12A to 12D is set constant. As a modification of theactuator, it is possible for each of the driving electrodes 12A to 12Dof the driving electrode section 12 to be set not larger than ½ of thewidth of each of the driving electrodes 4 and 8 on the side of themovable section and for the arranging pitch of the driving electrodes12A to 12D to be set at ¼ of that of each of the driving electrodes 4and 8 on the side of the movable section, as shown in. FIGS. 8A to 8C.In the actuator of the particular construction, if the movable sections2A, 2B are attracted toward the driving electrodes 12A to 12D of thedriving electrode section 12, each of the driving electrodes 4 and 8 onthe side of the movable section is allowed to face two of the drivingelectrodes 12A to 12D, as shown in FIGS. 8A to 8C.

[0165] The operation of the actuator shown in FIGS. 8A to 8C will now bedescribed with reference to FIGS. 9A to 9F, FIGS. 10A to 10F and FIGS.11A to 11F.

[0166] (I) Operation mode I in which the first and second movablesections 2A, 2B are simultaneously moved to the left as shown in FIG. 8Ais performed as follows.

[0167] (1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are held connected to the ground. Under this condition,a voltage H is applied to the driving electrodes 12A and 12B as shown inFIGS. 9A and 9B. As a result, the driving electrodes 4, 8 on the side ofthe movable sections in the vicinity of the driving electrodes 12A, 12Bare attracted toward the driving electrodes 12A, 12B by an electrostaticforce, with the result that the driving electrodes 4, 8 on the side ofthe movable sections are attracted to the driving electrode 12A. Itfollows that the first and second movable sections 2A, 2B are movedtoward the glass plate 13.

[0168] (2) In the next step, the voltage of the driving electrodes 12Aand 12B is changed into a low level at time t1 as shown in FIGS. 9A and9B, and a voltage H is applied to the holding electrodes sections 14A,14B as shown in FIGS. 9E and 9F. It follows that a strong electrostaticforce is generated between the holding electrode section 14A and thefixing electrode 5 on the side of the movable section 2A. As a result,the first movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section 2A is attracted tothe holding electrode section 14A. Also, a strong electrostatic force isgenerated between the holding electrode section 14B and the fixingelectrode 11 on the side of the movable section 2B. As a result, thesecond movable section 2B is moved toward the glass plate 15, and thefixing electrode 11 on the side of the movable section is attracted tothe holding electrode section 14B.

[0169] (3) In the next step, the voltage of the holding electrodesections 14A, 14B is changed into a low level L at time t2 as shown inFIGS. 9E and 9F, and a voltage H is applied to the driving electrodes12B and 12C as shown in FIGS. 9B and 9C. As a result, the drivingelectrodes 4, 8 on the side of the movable sections 2A, 2B in thevicinity of the driving electrodes 12B, 12C are attracted toward thedriving electrodes 12B, 12C by an electrostatic force, and the drivingelectrodes 4, 8 on the side of the movable sections 2A, 2B are attractedto the driving electrodes 12B, 12C. It follows that the first and secondmovable sections 2A, 2B are moved toward the glass plate 13. In thiscase, the first and second movable sections 2A, 2B are moved to theright in FIG. 8A by a distance equal to one stripe of the drivingelectrode section 12, i.e., a distance equal to one pitch, compared withthe position described in item (1) above.

[0170] (4) In the next step, the voltage of the driving electrodes 12Band 12C is changed into a low level L at time t3, and a voltage H isapplied again to the holding electrodes sections 14A, 14B as shown inFIGS. 9E and 9F. It follows that a strong electrostatic force isgenerated between the holding electrode section 14A and the fixingelectrode 5 on the side of the movable section 2A. As a result, thefirst movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section 2A is attracted tothe holding electrode section 14A. Also, a strong electrostatic force isgenerated between the holding electrode section 14B and the fixingelectrode 11 oh the side of the movable section 2B. As a result, thesecond movable section 2B is moved toward the glass plate 15, and thefixing electrode 11 on the side of the movable section 2B is attractedto the holding electrode section 14B.

[0171] (5) Further, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t4, and a voltage is appliedto the driving electrodes 12C and 12D as shown in FIGS. 9C and 9D. As aresult, the driving electrodes 4, 8 on the side of the movable sectionsin 2A, 2B the vicinity of the driving electrodes 12C, 12D are attractedtoward the driving electrodes 12C, 12D by an electrostatic force, andthe driving electrodes 4, 8 on the side of the movable sections 2A, 2Bare attracted to the driving electrodes 12C, 12D. It follows that thefirst and second movable sections 2A, 2B are moved toward the glassplate 13. In this case, the first and second movable sections 2A, 2B aremoved to the right in FIG. 8A by a distance equal to two stripes of thedriving electrode section 12, i.e., a distance equal to two pitches,compared with the position described in item (1) above.

[0172] (6) In the next step, the voltage of the driving electrodes 12Cand 12D is changed into a low level L at time t5, and a voltage isapplied again to the holding electrodes sections 14A, 14B as shown inFIGS. 9E and 9F. It follows that a strong electrostatic force isgenerated between the holding electrode section 14A and the fixingelectrode 5 on the side of the movable section 2A. As a result, thefirst movable section 2A is moved toward the glass plate 15, and thefixing electrode 5 on the side of the movable section 2A is attracted tothe holding electrode section 14A. Also, a strong electrostatic force isgenerated between the holding electrode section 14B and the fixingelectrode 11 on the side of the movable section 2B. As a result, thesecond movable section 2B is moved toward the glass plate 15, and thefixing electrode 11 on the side of the movable section 2B is attractedto the holding electrode section 14B.

[0173] (7) In the next step, the voltage of the holding electrodesections 14A, 14B is changed into a low level L at time t6, and avoltage H is applied to the driving electrodes 12D and 12A as shown inFIGS. 9D and 9A. As a result, the driving electrodes 4, 8 on the side ofthe movable sections 2A, 2B in the vicinity of the driving electrodes12D, 12A are attracted toward the driving electrode stripes 12B, 12A byan electrostatic force, and the driving electrodes 4, 8 on the side ofthe movable sections 2A, 2B are attracted to the driving electrodes 12D,12A. It follows that the first and second movable sections 2A, 2B aremoved toward the glass plate 13. In this case, the first and secondmovable sections 2A, 2B are moved to the right in FIG. 8A by a distanceequal to three stripes of the driving electrode section 12, i.e., adistance equal to three pitches, compared with the position described initem (1) above.

[0174] (8) In the next step, the voltage of the driving electrodes 12D,12A is changed into a low level L at time t7, and a voltage H is appliedagain to the holding electrodes sections 14A, 14B as shown in FIGS. 9Eand 9F. It follows that a strong electrostatic force is generatedbetween the holding electrode section 14A and the fixing electrode 5 onthe side of the movable section 2A. As a result, the first movablesection 2A is moved toward the glass plate 15, and the fixing electrode5 on the side of the movable section is attracted to the holdingelectrode section 14A. Also, a strong electrostatic force is generatedbetween the holding electrode section 14B and the fixing electrode 11 onthe side of the movable section 2B. As a result, the second movablesection 2B is moved toward the glass plate 15, and the fixing electrode11 on the side of the movable section 2B is attracted to the holdingelectrode section 14B.

[0175] (9) Further, the voltage of the holding electrode sections 14A,14B is changed into a low level L at time t8, and a voltage is appliedagain to the driving electrodes 12A and 12B as shown in FIGS. 9A and 9B.As a result, the driving electrodes 4, 8 on the side of the movablesections 2A, 2B in the vicinity of the driving electrodes 12A and 12Bare attracted toward the driving electrodes 12A and 12B by anelectrostatic force, and the driving electrodes 4, 8 on the side of themovable sections 2A, 2B are attracted to the driving electrodes 12A and12B. It follows that the first and second movable sections 2A, 2B aremoved toward the glass plate 13. In this case, the first and secondmovable sections 2A, 2B are moved to the left in FIG. 8A by a distanceequal to four stripes of the driving electrode section 12, i.e., adistance equal to four pitches, compared with the position described initem (1) above.

[0176] The steps of items (1) to (9) described above are repeated so asto move the first and second movable sections 2A, 2B by a desireddistance.

[0177] (II) Where the first and second movable sections 2A, 2B are movedto the right in FIG. 4A, the steps of operation mode I described aboveare carried out in the opposite direction. To be more specific, thesteps in items (9), (8), (7), (6), (5), (4), (3), (2) and (1) foroperation mode I described above are carried out in the order mentionedso as to move the first and second movable sections 2A, 2B to the leftin FIG. 8A by a desired distance.

[0178] (III) Operation to move the second movable section 2B alone tothe left or to the right with the first movable section 2A heldstationary.

[0179] Let us describe first the case where the second movable section2B is moved to the right as shown in FIG. 8B.

[0180] (1) In the first step, the driving electrodes 4, 8 of the movablesections 2A., 2B are held connected to the ground. Under this condition,a voltage is applied to the holding electrode section 14B as shown inFIG. 10F. As a result, an electrostatic force is generated between theholding electrode section 14B and the fixing electrode 5 on the side ofthe movable section. It follows that the second movable section 2B ismoved toward the glass plate 15, and the fixing electrode 5 on the sideof the movable section is attracted to the holding electrode section14B. In this case, the first movable section 2A is moved toward any ofthe glass plates 13, 15 and fixed temporarily. Where a voltage isapplied to the holding electrode section 14A as shown in FIG. 10E, thefirst movable section 2A is attracted to the glass plate 15 andcontinues to be fixed.

[0181] (2) In the next step, a voltage H is applied to the drivingelectrodes 12A and 12B at time t1 as shown in FIGS. 10A and 10B, withthe voltage H kept applied to the holding electrode section 14A as shownin FIG. 10E. As a result, the driving electrode 8 on the side of themovable section 2B in the vicinity of the driving electrodes 12A and 12Bare attracted toward the driving electrodes 12A and 12B by anelectrostatic force, and the driving electrode 8 on the side of themovable section 2B are attracted to the driving electrodes 12A and 12B.It follows that the second movable section 2B is moved toward the glassplate 13. On the other hand, since the voltage H is kept applied to theholding electrode 14A, the first movable section 2A is kept fixed on theside of the glass plate 15.

[0182] (3) In the next step, a voltage H is applied to the holdingelectrode 14B at time t2 as shown in FIG. 10F, with the voltage keptapplied to the holding electrode 14A. As a result, a strongelectrostatic force is generated between the holding electrode 14B andthe fixing electrode 11 on the side of the movable section 2B. Itfollows that the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable section2B is attracted to the holding electrode 14B.

[0183] (4) In the next step, a voltage H is applied to the drivingelectrodes 12B and 12C at time t3 as shown in FIGS. 10B and 10C, withthe voltage kept applied to the holding electrode 14A. As a result, thedriving electrode 8 on the side of the movable section 2B in thevicinity of the driving electrodes 12B and 12C is attracted toward thedriving electrodes 12B and 12C by an electrostatic force, with theresult that the driving electrode 8 on the side of the movable section2B is attracted to the driving electrodes 12B and 12C. It follows thatthe second movable section 2B is moved toward the glass plate 13. On theother hand, the first movable section 2A is similarly kept fixed on theside of the glass plate 15. In this case, the second movable section 2Bis moved to the right in FIG. 8B by a distance equal to one stripe ofthe driving electrode section 12, i.e., a distance equal to one pitch,compared with the position described in item (1) above.

[0184] (5) In the next step, a voltage H is applied to the holdingelectrode 14B at time t4 as shown in FIG. 10F, with the voltage keptapplied to the holding electrode 14A. As a result, a strongelectrostatic force is generated between the holding electrode 14B andthe fixing electrode 11 on the side of the movable section 2B. Itfollows that the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable section2B is attracted to the holding electrode section 14B.

[0185] (6) In the next step, a voltage is applied to the drivingelectrodes 12C electrodes 12C and 12D at time t5 as shown in FIGS. 10Cand 10D, with the voltage kept applied to the holding electrode 14A. Asa result, the driving electrode 8 on the side of the movable section 2Bin the vicinity of the driving electrodes 12C electrodes 12C and 12D isattracted toward the driving electrodes 12C by an electrostatic force,with the result that the driving electrode 8 on the side of the movablesection 2B is attracted to the driving electrodes 12C electrodes 12C and12D. It follows that the second movable section 2B is moved toward theglass plate 13. On the other hand, the first movable section 2A issimilarly kept fixed on the side of the glass plate 15. In this case,the second movable section 2B is moved to the right in FIG. 8B by adistance equal to two stripes of the driving electrode section 12, i.e.,a distance equal to two pitches, compared with the position described initem (1) above.

[0186] (7) In the next step, a voltage H is applied to the holdingelectrode 14B at time t6 as shown in FIG. 10F, with the voltage keptapplied to the holding electrode 14A. As a result, a strongelectrostatic force is generated between the holding electrode 14B andthe fixing electrode 11 on the side of the movable section 2B. Itfollows that the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable section2B is attracted to the holding electrode section 14B.

[0187] (8) In the next step, a voltage is applied to the drivingelectrodes 12D and 12A at time t7 as shown in FIGS. 10D and 10A, withthe voltage kept applied to the holding electrode 14A. As a result, thedriving electrode 8 on the side of the movable section in the vicinityof the driving electrodes 12D and 12A is attracted toward the drivingelectrodes 12D and 12A by an electrostatic force, with the result thatthe driving electrode 8 on the side of the movable section is attractedto the driving electrodes 12D and 12A. It follows that the secondmovable section 2B is moved toward the glass plate 13. On the otherhand, the first movable section 2A is similarly kept fixed on the sideof the glass plate 15. In this case, the second movable section 2B ismoved to the right in FIG. 8B by a distance equal to three stripes ofthe driving electrode section 12, i.e., a distance equal to threepitches, compared with the position described in item (1) above.

[0188] (9) In the next step, a voltage is applied to the holdingelectrode 14B at time t8 as shown in FIG. 10F, with the voltage keptapplied to the holding electrode section 14A. As a result, a strongelectrostatic force is generated between the holding electrode section14B and the fixing electrode 11 on the side of the movable section. Itfollows that the second movable section 2B is moved toward the glassplate 15, and the fixing electrode 11 on the side of the movable sectionis attracted to the holding electrode section 14B.

[0189] (10) Further, a voltage is applied to the driving electrodes 12Aand 12B at time t9 as shown in FIGS. 10A and 10B, with the voltage keptapplied to the holding electrode 14A. As a result, the driving electrode8 on the side of the movable section in the vicinity of the drivingelectrodes 12A and 12B is attracted toward the driving electrodes 12Aand 12B by an electrostatic force, with the result that the drivingelectrode 8 on the side of the movable section is attracted to thedriving electrodes 12A and 12B. It follows that the second movablesection 2B is moved toward the glass plate 13. On the other hand, thefirst movable section 2A is similarly kept fixed on the side of theglass plate 15. In this case, the second movable section 2B is moved tothe right in FIG. 8B by a distance equal to four stripes of the drivingelectrode section 12, i.e., a distance equal to four pitches, comparedwith the position described in item (1) above.

[0190] The steps of items (1) to (10) described above are repeated so asto move the second movable sections 2B by a desired distance.

[0191] Where it is desired to move the second movable section 2B to theright, the steps of operation mode III described above are carried outin the order of items (1), (10), (9), (8), (7), (6), (5), (4), (3) and(2) described above so as to move the second movable section 2B to theright by a desired distance.

[0192] (IV) Operation to move the first movable section 2A alone to theleft or to the right with the second movable section 2B held stationary.

[0193] Let us describe first the case where the first movable section 2Ais moved to the right as shown in FIG. 8C.

[0194] (1) In the first step, the driving electrodes 4, 8 of the movablesections 2A, 2B are held connected to the ground. Under this condition,a voltage is applied to the holding electrode section 14A as shown inFIG. 11E. As a result, an electrostatic force is generated between theholding electrode section 14A and the fixing electrode 11 on the side ofthe movable section 2A. It follows that the first movable section 2A ismoved toward the glass plate 15, and the fixing electrode 5 on the sideof the movable section 2A is attracted to the holding electrode section14A. Where a voltage is applied to the holding electrode section 14B asshown in FIG. 11F, the second movable section 2B is attracted to theglass plate 15 and continues to be fixed.

[0195] (2) In the next step, a voltage H is applied to the drivingelectrodes 12A and 12B at time t1 as shown in FIGS. 11A and 11B, withthe voltage H kept applied to the holding electrode section 14B as shownin FIG. 11F. As a result, the driving electrode 4 on the side of themovable section 2A in the vicinity of the driving electrodes 12A and 12Bis attracted toward the driving electrodes 12A and 12B by anelectrostatic force, and the driving electrode 4 on the side of themovable section 2A is attracted to the driving electrodes 12A and 12B.It follows that the first movable section 2A is moved toward the glassplate 13. On the other hand, since the voltage H is kept applied to theholding electrode 14B, the second movable section 2B is kept fixed onthe side of the glass plate 15.

[0196] (3) In the next step, a voltage H is applied to the holdingelectrode 14A at time t2 as shown in FIG. 1E, with the voltage keptapplied to the holding electrode 14B. As a result, a strongelectrostatic force is generated between the holding electrode 14A andthe fixing electrode 5 on the side of the movable section 2A. It followsthat the first movable section 2A is moved toward the glass plate 15,and the fixing electrode 5 on the side of the movable section isattracted to the holding electrode 14A.

[0197] (4) In the next step, a voltage H is applied to the drivingelectrodes 12B and 12C at time t3 as shown in FIGS. 11B and 11C, withthe voltage kept applied to the holding electrode 14B. As a result, thedriving electrode 4 on the side of the movable section 3A in thevicinity of the driving electrodes 12B and 12C is attracted toward thedriving electrodes 12B and 12C by an electrostatic force, with theresult that the driving electrode 4 on the side of the movable section2A is attracted to the driving electrodes 12B and 12C. It follows thatthe first movable section 2A is moved toward the glass plate 13. On theother hand, the second movable section 2B is similarly kept fixed on theside of the glass plate 15. In this case, the first movable section 2Ais moved to the right in FIG. 8C by a distance equal to one stripe ofthe driving electrode section 12, i.e., a distance equal to one pitch,compared with the position described in item (1) above.

[0198] (5) In the next step, a voltage H is applied to the holdingelectrode 14A at time t4 as shown in FIG. 11E, with the voltage keptapplied to the holding electrode 14B. As a result, a strongelectrostatic force is generated between the holding electrode 14A andthe fixing electrode 5 on the side of the movable section. It followsthat the first movable section 2A is moved toward the glass plate 15,and the fixing electrode 5 on the side of the movable section 2A isattracted to the holding electrode section 14A.

[0199] (6) In the next step, a voltage H is applied to the drivingelectrodes 12C electrodes 12C and 12D at time t5 as shown in FIGS. 11Cand 11D, with the voltage H kept applied to the holding electrode 14B.As a result, the driving electrode 4 on the side of the movable section2A in the vicinity of the driving electrode strip 2A, 2B is attractedtoward the driving electrodes 12C by an electrostatic force, with theresult that the driving electrode 4 on the side of the movable section2A is attracted to the driving electrodes 12C electrodes 12C and 12D. Itfollows that the first movable section 2A is moved toward the glassplate 13. On the other hand, the second movable section 2B is similarlykept fixed on the side of the glass plate 15. In this case, the firstmovable section 2A is moved to the right in FIG. 4A by a distance equalto two stripes of the driving electrode section 12, i.e., a distanceequal to two pitches, compared with the position described in item (1)above.

[0200] (7) In the next step, a voltage H is applied to the holdingelectrode 14A at time t6 as shown in FIG. 1E, with the voltage H keptapplied to the holding electrode 14B. As a result, a strongelectrostatic force is generated between the holding electrode 14A andthe fixing electrode 5 on the side of the movable section. It followsthat the first movable section 2A is moved toward the glass plate 15,and the fixing electrode 5 on the side of the movable section isattracted to the holding electrode section 14A.

[0201] (8) In the next step, a voltage H is applied to the drivingelectrodes 12D and 12A at time t7 as shown in FIGS. 11D and 11A, withthe voltage H kept applied to the holding electrode 14B. As a result,the driving electrode 4 on the side of the movable section 2A in thevicinity of the driving electrodes 12D and 12A is attracted toward thedriving electrodes 12D and 12A by an electrostatic force, with theresult that the driving electrode 4 on the side of the movable sectionis attracted to the driving electrodes 12D and 12A. It follows that thefirst movable section 2A is moved toward the glass plate 13. On theother hand, the second movable section 2B is similarly kept fixed on theside of the glass plate 15. In this case, the first movable section 2Ais moved to the right in FIG. 4A by a distance equal to three stripes ofthe driving electrode section 12, i.e., a distance equal to threepitches, compared with the position described in item (1) above.

[0202] (9) In the next step, a voltage H is applied to the holdingelectrode 14A at time t8 as shown in FIG. 11E, with the voltage H keptapplied to the holding electrode 14B. As a result, a strongelectrostatic force is generated between the holding electrode section14A and the fixing electrode 5 on the side of the movable section. Itfollows that the first movable section 2A is moved toward the glassplate 15, and the fixing electrode 5 on the side of the movable sectionis attracted to the holding electrode section 14A.

[0203] (10) Further, a voltage H is applied to the driving electrodes12A and 12B at time t9 as shown in FIGS. 11A and 11B, with the voltagekept applied to the holding electrode 14B. As a result, the drivingelectrode 4 on the side of the movable section in the vicinity of thedriving electrodes 12A and 12B is attracted toward the drivingelectrodes 12A and 12B by an electrostatic force, with the result thatthe driving electrode 4 on the side of the movable section is attractedto the driving electrodes 12A and 12B. It follows that the first movablesection 2A is moved toward the glass plate 13. On the other hand, thesecond movable section 2B is temporarily kept fixed on the side of theglass plate 15. In this case, the first movable section 2A is moved tothe right in FIG. 8C by a distance equal to four stripes of the drivingelectrode section 12, i.e., a distance equal to four pitches, comparedwith the position described in item (1) above.

[0204] The steps of items (1) to (10) described above are repeated so asto move the first movable section 2A by a desired distance.

[0205] Where it is desired to move the first movable section 2A to theright, the steps of operation mode III described above are carried outin the order of items (1), (10), (9), (8), (7), (6), (5), (4), (3) and(2) described above so as to move the first movable section 2A to theright by a desired distance.

[0206] The relationship between the positions of the first and secondmovable sections 2A, 2B and the zooming magnification (magnification ofenlargement or reduction) of the lens system will now be described withreference to FIGS. 12A and 12B.

[0207] In general, a signal supplied by the user to the input section,e.g., a button or a knob, of an apparatus such as a PDA mounted to theelectrostatic actuator is forwarded to a control unit 19 within theapparatus. The control signal for the zooming is formed in the controlunit 19 based on the input signal. The first and second movable sections2A, 2B are driven in accordance with the control signal.

[0208]FIG. 12A is a vertical cross sectional view showing anelectrostatic actuator, and FIG. 12B is a graph showing the relationshipbetween the positions in the axial direction of the first and secondmovable sections 2A, 2B and the optical magnification. Curve P in FIG.12B denotes the moving range of the first movable section 2A, and line Qdenotes the moving range of the second movable section 2B. As apparentfrom FIG. 12B, there is an overlapping region in the moving ranges ofthe first and second movable sections 2A and 2B in substantially thecentral portion of the stator 3. Incidentally, in the graph of FIG. 12B,the origin of the abscissa is set at one open portion of the stator 3 ofthe electrostatic actuator on the side of which the first movablesection 2A is mounted.

[0209] As shown in FIG. 12A, a CCD sensor 17 is arranged on a fixedplate 18 on the image forming plane of the lenses 6 and 9 in the otheropen portion of the stator 3 on the side of which the second movablesection 2B is mounted, and the fixed plate 18 is fixed to the other openportion of the stator 3.

[0210] Also, as shown in FIG. 12B, where the optical system is set at acertain optical magnification X, the first movable section 2A isarranged in a point E and the second movable section 2B is arranged inanother point F. Likewise, where the optical system is set at an opticalmagnification Y larger than the optical magnification X, the firstmovable section 2A is set at a point G and the second movable section 2Bis set at a point H. Further, where the optical system is set at anoptical magnification Z larger than the optical magnification Y, thefirst movable section 2A is set at a point I and the second movablesection 2B is set at a point J.

[0211] Where the first and second movable sections 2A, 2B are moved todesired positions relative to a desired optical magnification, the firstand second movable sections 2A, 2B are roughly moved first, followed byfixing one of the first and second movable sections 2A, 2B and finelymoving the other movable section, which is movable, so as to set theposition of the movable section, which is movable, at a desiredposition. Then, the movable section whose position has been set isfixed, and the other movable section is finely moved so as to be set ata desired position (fine operation).

[0212] The operations described above are performed by the stepsdescribed previously in conjunction with the operation modes I to IV soas to move independently the first and second movable sections 2A and2B, thereby setting the optical system at a desired magnification.

[0213] In the embodiment described above, the first and second movablesections 2A, 2B are roughly moved first, followed by fixing one movablesection and finely moving the other movable section so as to be set at adesired position, thereby setting the optical system at a desiredoptical magnification. Alternatively, it is also possible to move thefirst and second movable sections 2A, 2B directly to the desiredpositions by independently controlling the first and second movablesections 2A, 2B without fixing one of the first and second movablesections 2A, 2B in the midway of setting the positions of these firstand second movable sections 2A, 2B so as to obtain a desired opticalmagnification. Where the first movable section 2A is temporarily movedtoward the driving electrode section 12 or is temporarily fixed on theside of the driving electrode section 12 in the particular operation,the second movable section 2B is moved toward the holding electrodesection 14B or is temporarily fixed to the holding electrode section 14Bwithout fail. In the latter case, however, the time required for themagnification or reduction is rendered somewhat longer than that in theformer case.

[0214] In the first embodiment described above, a plurality of movablesections for magnifying or reducing the photographed image areindependently operated so as to obtain a desired optical magnification.

[0215] An electrostatic actuator according to a second embodiment of thepresent invention will now be described with reference to FIGS. 13A to13C.

[0216] In each of the embodiments described below, the same constituentsof the electrostatic actuator are denoted by the same reference numeralsso as to avoid an overlapping description.

[0217] In the electrostatic actuator according to the second embodimentof the present invention, the holding electrodes 5, 11 on the side ofthe movable sections are formed in substantially the entire regions ofthe lower surfaces of the first and second movable sections 2A, 2B.

[0218]FIG. 13A is a side view schematically showing the movable sectionsof the electrostatic actuator according to the second embodiment of thepresent invention. FIG. 13B is a plan view schematically showing thelower surfaces of the movable sections shown in FIG. 13A. Further, FIG.13C is a plan view directed to the glass plate of the electrostaticactuator according to the second embodiment of the present invention andschematically showing the upper surface of the glass plate on which themovable sections shown in FIG. 13A are slid.

[0219] The fixing electrode 5 on the side of the movable section, whichis shaped as shown in FIG. 13B, is mounted to the lower surface of thefirst movable section 2A shown in FIG. 13A. The fixing electrode 5 onthe side of the movable section extends planar on the lower surface ofthe first movable section 2A and is substantially in the form of a combhaving three projecting regions projecting toward the second movablesection 2B and two recessed regions sandwiched between the adjacentprojecting regions.

[0220] As shown in FIG. 13B, the fixing electrode 11 on the side of themovable section is mounted to the lower surface of the second movablesection 2B. The fixing electrode 11 on the side of the movable sectionextends planar on the lower surface of the second movable section 2B andis substantially in the form of a comb having three recessed regions onthe side of the first movable section 2A and two projecting regionssandwiched between the adjacent recessed regions. As apparent from FIG.13B, the holding electrodes 5, 11 on the side of the movable sectionsare formed complementary such that the recessed regions of one of theseholding electrodes 5, 11 are engaged with the projecting regions of theother of these holding electrodes 5, 11.

[0221] As shown in FIG. 13C, the holding electrode sections 14A, 14Bextend planar such that these holding electrode sections 14B, 14B areelectrically separated from each other in the central portion of theglass plate 15 and are shaped in the central portion of the glass plate15 to conform with the shapes of the holding electrodes 5, 11 on theside of the movable sections, respectively. To be more specific, theholding electrode sections 14A, 14B are shaped complementary in thecentral portion of the glass plate 15 such that the recessed regions ofone of these holding electrode sections 14A, 14B are engaged with theprojecting regions of the other of these holding electrode sections 14A,14B. The electrostatic actuator of the particular construction isoperated in a manner similar to that of the electrostatic actuator shownin FIG. 4A. It should be noted, however, that the holding electrode 14Afor temporarily fixing the first movable section 2A on the side of theplate 15 is formed to extend to only about the central portion of theglass plate 15. Also, the holding electrode section 14B for temporarilyfixing the second movable section 2B on the side of the glass plate 15is formed in that region of the glass plate 15 in which the holdingelectrode section 14A is not formed in a manner to extend to only aboutthe central portion of the glass plate 15. It follows that the firstmovable section 2A is capable of movement from the open portion to onlyabout the central portion of the glass plate 15. Likewise, the secondmovable section 2B is capable of movement from the CCD sensor 17 to onlyabout the central portion of the glass plate 15.

[0222] It should also be noted that, during the period between the timewhen the movement of the first and second movable sections 2A, 2B isfinished and the time when the first and second movable sections 2A, 2Bnewly begin to be moved, the first movable section 2A continues to betemporarily fixed to any of the driving electrode sections 12 and 14A,and the second movable section 2B continues to be temporarily fixed toany of the driving electrode sections 12 and 14B. Under the fixed state,an electric current is supplied from the internal power source so as topermit the first and second movable sections 2A, 2B to continue to befixed to the driving electrode sections even if the main power source ofthe apparatus having the electrostatic actuator mounted thereto isturned off.

[0223] As described above, in the electrostatic actuator according tothe second embodiment of the present invention, a plurality of movablesections for magnifying or reducing the photographed image areindependently operated so as to obtain a desired optical magnification.

[0224] It should also be noted that the moving ranges of the first andsecond movable sections are smaller than those in the first embodimentdescribed previously. However, the possibility of the breakage caused bythe mutual contact of the first and second movable sections 2A, 2B canbe eliminated in the second embodiment of the present invention so as toimprove the reliability of the electrostatic actuator.

[0225] An electrostatic actuator according to a third embodiment of thepresent invention will now be described with reference to FIGS. 14A to14C.

[0226] In the electrostatic actuator shown in FIG. 14B, each of theholding electrodes 5, 11 on the side of the movable sections is formedin the shape of a flat plate.

[0227]FIG. 14A is a side view schematically showing the movable sectionsin the electrostatic actuator according to the third embodiment of thepresent invention. FIG. 14B is a plan view schematically showing thelower surfaces of the movable sections shown in FIG. 14A. Further, FIG.14C is a plan view schematically showing the upper surface of the glassplate included in the electrostatic actuator according to the thirdembodiment of the present invention.

[0228] As shown in the left side portion of FIG. 14B, the fixingelectrode 5 on the side of the movable section is formed in the shape ofa flat plate. It should be noted, however, that the fixing electrode 5on the side of the movable section has an area larger than at least halfthe area of the lower surface of the first movable section 2A and isformed not to extend over the entire region of the lower surface of thefirst movable section 2A. For example, the fixing electrode 5 on theside of the movable section is arranged away from the movable section 2Bin a deviated manner in a predetermined direction.

[0229] The fixing electrode 11 on the side of the movable section isformed in the shape of a flat plate in the right portion of FIG. 14C. Itshould be noted, however, that the fixing electrode 11 on the side ofthe movable section has an area larger than at least half the area ofthe lower surface of the second movable section 2B and is formed not toextend over the entire region of the lower surface of the second movablesection 2B. For example, the fixing electrode 11 on the side of themovable section is formed away from the first movable section 2A in adeviated manner on the side opposite to the predetermined directionnoted above.

[0230] Further, the holding electrode sections 14A, 14B are formed toextend planar as shown in FIG. 14C. In other words, the two planarholding electrode sections 14A, 14B are formed apart from each other onthe glass plate 15. The areas of the rectangular holding electrodesections 14A, 14B are set in accordance with the moving range (opticalmagnification) of each of the movable sections. It is possible for theseareas to be substantially equal to each other or different from eachother. Also, the holding electrode section 14A, for example, is arrangedon the glass plate 15 in a deviated manner in a predetermined direction,and the holding electrode section 14B is arranged on the glass plate 15in a deviated manner on the side opposite to the predetermined directednoted above.

[0231] The electrostatic actuator of the construction described above isoperated in substantially the same manner as that of the electrostaticactuator according to the first embodiment of the present invention.Also, the first and second movable sections 2A, 2B can be moved onlywithin the ranges in which the holding electrode sections 14A, 14B areformed as in the electrostatic actuator according to the secondembodiment of the present invention. It should also be noted that,during the period between the time when the movement of the first andsecond movable sections 2A, 2B is finished and the time when the firstand second movable sections 2A, 2B begin to be newly moved, the firstmovable section 2A continues to be temporarily fixed to any of thedriving electrode sections 12, 14A, and the second movable section 2Bcontinues to be temporarily fixed to any of the driving electrodesections 12, 14B. The fixed state continues to be maintained by theelectric current supplied from the internal power source even if themain power source of the apparatus having the electrostatic actuatormounted thereto is turned off.

[0232] In the electrostatic actuator of the construction describedabove, the movable sections for magnifying or reducing the photographedimage are moved independently so as to obtain a desired opticalmagnification.

[0233] Also, the moving ranges of the first and second movable sections2A, 2B are rendered smaller than those in the first embodiment of thepresent invention. However, the possibility of the breakage caused bythe mutual contact of the first and second movable sections 2A, 2B iseliminated so as to improve the reliability of the electrostaticactuator.

[0234] It should also be noted that each of the holding electrodesections 14A, 14B is in the shape of a rectangular flat plate. Thisfacilitates the manufacture of the holding electrode sections 14A, 14Bso as to contribute to the reduction in the manufacturing cost.

[0235] The methods of manufacturing the first and second movablesections 2A, 2B and the stator 3 in each of the first to thirdembodiments described above will now be described with reference toFIGS. 15A to 19.

[0236] The method of manufacturing the stator 3 will be described firstwith reference to FIGS. 15A to 15C.

[0237]FIG. 15A is a plan view showing in a developed fashion the partsof the movable section. FIG. 15B is an oblique view showing theassembled state of the movable section shown in FIG. 15A. FIG. 15C is aplan view schematically showing the state that the parts of the movablesection are mounted to a mold in the process of manufacturing a statorframe. Further, FIG. 15D is an oblique view schematically showing themovable section manufactured through the step shown in FIG. 15C.

[0238] As shown in FIG. 15A, the parts of the first movable section 2Acomprise a first flat plate 20 having the electrode 4 mounted thereto, asecond flat plate 21 having the electrode 5 mounted thereto, an arcuatefirst connecting member 22 for connecting the first flat plate 20 andthe second flat plate 21 to each other, an arcuate second connectingmember 23, and an abutting member 24 attached to the first flat plate20. The driving electrode 4 on the side of the movable section, whichhas a concave-convex configuration, and the fixing electrode 5 on theside of the movable section is formed by etching on the surfaces of thefirst flat plate 20 and the second flat plate 21, respectively. Thefirst flat plate 20, the second flat plate 21, the first connectingmembers 22, 22, the second connecting members 23, 23, and the abuttingmember 24 are integrally formed by a press molding from a metal plate.

[0239] The parts of the first movable section 2A are assembled by thefolding as shown in FIG. 15B. Specifically, the connecting portionbetween the first flat plate 20 and the first connecting members 22, 22,the connecting portion between the second flat plate 21 and the firstconnecting members 22, 22, the connecting portion between the secondflat plate 21 and the second connecting members 23, 23, and theconnecting portion between the second connecting members 23, 23 and theabutting member 24 are folded such that the driving electrode 4 on theside of the movable section and the fixing electrode 5 on the side ofthe movable section are arranged on the outside. After the folding, theabutting member 24 is bonded to the first flat plate 20 by, for example,a spot welding. The first connecting members 22, 22 and the secondconnecting members 23, 23 are capable of elastically receiving thepressure from the outside, with the result that the movable section isconstructed flexible.

[0240] In the next step, the parts of the first movable section 2A arefixed by a resin as shown in FIG. 15C.

[0241] For fixing the first movable section 2A, used are molds 25A, 25B,25C and 25D, which can be separated into four parts. The convex portionsof the driving electrode 4 on the side of the movable section and thefixing electrode 5 on the side of the movable section are allowed toabut against the inner surfaces of the molds 25A, 25B and, thus, concaverecessed spaces are formed on the inner surfaces of the molds 25A, 25B.The mold 25C is fixed in a sandwiched fashion between the molds 25A and25B. Convex portions in which the lens 6 having a stepped shape isfitted are formed in the outer surfaces of the mold 25C facing the innerwalls of the molds 25A, 25B. The mold 25D is also fixed in a sandwichedfashion between the molds 25A and 25B and positioned to face the mold25C. The mold 25D is arranged to abut against the mold 25C and to beapart from those regions of the first and second flat plates 20, 21 inwhich the driving electrode 4 on the side of the movable section and thefixing electrode 5 on the side of the movable section are not arranged.

[0242] In the first step, the molds 25A and 25B are arranged in contactwith the driving electrode 4 on the side of the movable section and theconvex portion of the fixing electrode 5 on the side of the movablesection of the first movable section 2A. Then, the molds 25C and 25D areinserted into the clearance between the molds 25A and 25B in a manner toclose the up-down direction of the first movable section 2A. As aresult, the first movable section 2A is covered with the molds 25A to25D. In this step, the first flat plate 20 and the second flat plate 21are urged against the molds 25A, 25B by the connecting members 22, 22,23, 23. The molds 25A to 25D are fixed so as not to be moved.

[0243] In the next step, a resin is introduced into the clearancethrough a resin-introducing hole 26 communicating with a part of themold 25B. In this step, the molds 25A to 25D are maintained at about150° C. by a heating means such as a heater, and the resin is pouredinto the clearance under a state maintained at about 300° C. After thepouring of the resin, the poured resin is gradually cooled with time toabout room temperature so as to be solidified. By the solidification ofthe resin, the first movable section 2A is fixed without being moved bythe connecting members 22, 22, 23, 23.

[0244] It should be noted that, in this stage, the first and second flatplates 20, 21 are urged by a predetermined elastic force against themolds 25A, 25B, with the result that the first and second flat plates20, 21 are held apart from each other by a substantially predetermineddistance. As a result, the distance between the driving electrode 4 onthe side of the movable section and the fixing electrode 5 on the sideof the movable section of the first movable section 2A prepared bysolidifying the resin is held substantially constant. In addition, thenonuniformity in the manufacturing accuracy can be eliminated so as toobtain a plurality of first movable sections 2A having substantially thesame shape.

[0245] As shown in FIG. 15D, the lens 6 is mounted to one surface in theaxial direction of the first movable section 2A.

[0246] Incidentally, the second movable section 2B can also bemanufactured by a method similar to the method of manufacturing thefirst movable section 2A described above.

[0247] The resin to be introduced into the clearance is preferably amaterial having a conductive characteristics into which electricalconductive particles such as carbon particles are mixed to improve anreliability of the wiring on the movable sections 2A and 2B.

[0248] The manufacture of the stator frame 3 will now be described withreference to FIGS. 16A to 16C.

[0249] As shown in FIG. 16A, used are two separable molds 30A, 30B.Bores are formed in these molds 30A, 30B such that, when the molds 30Aand 30B are combined, the bores are allowed to conform with the outerconfiguration of the stator frame 3.

[0250] At the beginning, the molds 30A and 30B are in a separated state.

[0251] The glass plates 13, 15 each having a substantially U-shapedlateral cross section are arranged such that the back surfaces of theglass plates 13, 15 are brought into contact with the convex portions ofa pair of mutually facing surfaces 31A, 31B of the molds 30A, 30B,respectively. The patterned driving electrode section 12 and the holdingelectrode 14 are formed on the surfaces facing the back surfaces of theglass plates 13, 15 and arranged on the surfaces 31A, 31B of the molds30A, 30B, respectively, in a manner to permit the driving electrodesection 12 and the holding electrode section 14 to face each other. Itshould be noted that the glass plates 13, 15, in which the shapes ofthese electrodes are simplified, are shown in FIG. 16B.

[0252] The molds 30A and 30B are combined such that the side surfaces ofa parallelepiped core 32 shown in FIG. 16D are in contact with a surface31C, not in contact with a surface 31D, and in contact with edges 33 ofthe driving electrode section 12 and the holding electrode section 14.When the molds 30A and 30B are combined, the concave portions of thedriving electrode section 12 and the holding electrode section 14 arenot in contact with the concave portions of the core 32, the surface 31Dand the surface 31C. Incidentally, the details in the shapes of themolds 30A and 30B are partly omitted in FIG. 16C.

[0253] It should also be noted that the core 32 is not in contact withsurfaces 34A, 34B, and 34D and is in contact with the convex portion ofa surface 34C.

[0254] A resin having a conductivity such as a resin is poured into theclearance between the core 32 and the surfaces 34A to 34D. In thisstage, the molds 30A, 30B are kept heated to about 150° C. by a heatingmeans such as a heater, and the resin is poured into the clearance in astate held at about 300° C. After the pouring, the resin is graduallycooled with time to about room temperature so as to be solidified.

[0255] The core 32 is taken out a predetermined time later (aftercompletion of solidification of the resin), and the molds 30A and 30Bare separated from each other so as to obtain the stator 3 of a desiredshape.

[0256] The electrostatic actuator is prepared by combining the first andsecond movable sections 2A, 2B, the stator 3 and the glass plates 13, 15thus manufactured.

[0257] Another method of manufacturing the movable section will now bedescribed with reference to FIGS. 17A to 17C.

[0258] As shown in FIG. 17A, the driving electrode 4 on the side of themovable section is obtained by processing a silicon substrate. Theconcave-convex configuration of the driving electrode 4 on the side ofthe movable section is formed by an etching such that one surface of thesilicon substrate is allowed to bear a concave-convex configuration of adesired size, i.e., on the order of several microns. The etching methodis equal to the method employed for increasing the degree of integrationof an LSI. It is possible to employ any of the wet etching and the dryetching for forming the concave-convex configuration noted above.

[0259] As shown in FIG. 17B, a body 35 of the movable section isprepared by assembling a flat plate formed of a conductive resin into aparallelepiped state. The lens 6 is mounted in the axial direction ofthe body 35 of the movable section, and a pad 36 to which is connected aground wiring 7 connected to the ground is formed in a part of the sidesurface of the body 35 of the movable section.

[0260] As shown in FIG. 17C, the driving electrode 4 on the side of themovable section thus prepared is bonded to the body 35 of the movablesection, and the fixing electrode 5 is bonded to the upper surface ofthe body 35 of the movable section with an acrylic adhesive that iscured upon irradiation with an ultraviolet light so as to prepare thefirst movable section 2A.

[0261] An electrostatic actuator is manufactured by combining the firstmovable section 2A thus manufactured and the stator 3.

[0262] The method of manufacturing the movable section will now bedescribed with reference to FIG. 18.

[0263]FIG. 18 shows the method of manufacturing the movable section. Asshown in the drawing, molds 37A to 37D are combined, and a resin ispoured into the clearance among the molds 37A to 37D so as tomanufacture the first movable section 2A. Incidentally, the mold 37D hasa length reaching the mold 37C.

[0264] The resin poured into the clearance among the molds 37A to 37D isprepared by mixing carbon particles 38 with carbon fibers 39 each havingan electrical conductivity. Incidentally, the carbon particles 38 aresubstantially in the form of spheres each having a diameter of severalmicrons. On the other hand, the carbon fibers 39 are in the form of rodseach having a diameter of about 10 μm and a length of scores of microns.The first movable section 2A that is not provided with a lens isprepared by solidifying the particular resin.

[0265] According to the manufacturing method described above, the convexshapes of the driving electrode 4 on the side of the movable section andthe fixing electrode 5 on the side of the movable section of the firstmovable section 2A are formed at an interval of about 20 μm. Therefore,it is possible for the carbon fiber 39 not to enter the clearancebetween adjacent convex portions 40, i.e., not to enter a concaveportion 41. However, even if the carbon fiber does not enter the concaveportion 41, the carbon particle 38 mixed in the resin enters the concaveportion 41. It follows that it is possible to obtain the first movablesection 2A having a good conductivity.

[0266] The movable sections 2A, 2B may be made of a nonconductive resin.In these movable sections 2A, 2B, an electrical conductivity can beapplied to the movable sections with plating a conductive film on themovable sections 2A, 2B after the molding. This method have adisadvantage of increasing manufacturing steps, but according to thismanufacturing method, a good conductivity can be applied to the movablesections 2A, 2B.

[0267] Another method of manufacturing the movable section and thestator will now be described with reference to FIG. 19.

[0268]FIG. 19 shows the manufacturing method of the movable section andthe stator. As shown in the drawing, the first and second movablesections 2A, 2B and the stator 3 into which the first and second movablesections 2A, 2B are inserted are formed in a single mold 42A.Incidentally, FIG. 19 shows an example of the mold in which two statorsand two movable sections are formed.

[0269] The shape of the mold of the first and second movable sections2A, 2B is substantially equal to that shown in FIG. 18. Also, the shapeof the mold of the stator 3 is substantially equal to that shown in FIG.16A. The shapes of the driving electrode 4 on the side of the movablesection and the fixing electrode 5 on the side of the movable sectionare formed on a pair of mutually facing inner surfaces 43A, 43B of thefirst movable section 2A. Also, the shapes of the driving electrode 12and the holding electrode 14 are formed on a pair of mutually facinginner surfaces 44A, 44B of the mold of the stator 3.

[0270] By using the molds 42A, 42B of the particular construction, it ispossible to manufacture the first and second movable sections 2A, 2B andthe stator frame 3 low in the nonuniformity of the dimensional accuracyin a short time on the mass production basis.

[0271] Needless to say, the present invention is not limited to each ofthe embodiments described above and can be worked in variously modifiedfashions within the technical scope of the present invention. Forexample, it is possible to detect the positions of the two movablesections by an optical sensor and, if these two movable sections arelikely to collide against each other, it is possible to fix temporarilyone of these movable sections so as to avoid the collision.

[0272] Also, it is not absolutely necessary for two movable sections tobe inserted into the stator. It is possible for three or more movablesections to be inserted into the stator in order to obtain a desiredmagnification.

[0273] Further, the shapes of the first bonding member and the secondbonding member are not particularly limited as far as these bondingmembers are shaped to produce elastic characteristics.

[0274] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the present invention in itsbroader aspects is not limited to the specific details andrepresentative embodiments shown and described herein. Accordingly,various modifications may be made without departing from the spirit orscope of the general inventive concept as defined by the appended claimsand their equivalents.

What is claimed is:
 1. An electrostatic actuator, comprising: firststator electrodes arranged in a predetermined direction and extending ina direction crossing the predetermined direction; a second statorelectrode arranged to face the first stator electrodes and extending inthe predetermined direction; a third stator electrode arranged to facethe first stator electrodes and extending in the predetermined directionso as to be electrically isolated from the second stator electrode; afirst movable section provided with first and second movable sectionelectrodes, arranged movable within a moving space in the predetermineddirection, the moving space being defined between the first statorelectrodes and the second stator electrode, the first movable sectionelectrodes being mounted to the first movable section to face the firststator electrodes, and the second movable section electrode beingmounted to the first movable section to face the second statorelectrode; and a second movable section provided with third and fourthmovable section electrodes, arranged independently of the first movablesection, the second movable section being movable within the movingspace in the predetermined direction, the third movable sectionelectrodes being mounted to the second movable section to face the firststator electrodes, and the fourth movable section electrode beingmounted to the second movable section to face the third statorelectrode.
 2. The electrostatic actuator according to claim 1, furthercomprising first and second lenses arranged within the first and secondmovable sections, respectively.
 3. The electrostatic actuator accordingto claim 1, wherein the first stator electrodes, the first movablesection electrodes and the third movable section electrodes are arrangedsubstantially in parallel in substantially the same pitch and havesubstantially the same width.
 4. The electrostatic actuator according toclaim 1, wherein the first movable section electrodes and the thirdmovable section electrodes are arranged substantially in parallel insubstantially the same pitch and have substantially the same width. 5.The electrostatic actuator according to claim 4, wherein the firststator electrodes is arranged at a pitch equal to one-fourth of thearranging pitch of the first movable section electrodes and the thirdmovable section electrodes.
 6. The electrostatic actuator according toclaim 1, wherein the first movable section is capable of being moved inthe moving space in the predetermined direction with the fourth movablesection electrode being attracted to the third stator electrode so as tohold the second movable section.
 7. The electrostatic actuator accordingto claim 1, further comprising: a driving circuit configured to supplyfirst and second driving signals to the first and second statorelectrodes, respectively, to move the first movable section in thepredetermined direction, and to supply a holding voltage signal to thethird stator electrode to hold the second movable section.
 8. Anelectrostatic actuator comprising: a stator including a hollow statorframe having a space extending in a predetermined direction, the statorframe having a first inner surface extending in parallel to thepredetermined direction and a second inner surface facing the firstinner surface, first stator electrodes arranged in the predetermineddirection on the first inner surface and each of the stator electrodesextending in a direction crossing the predetermined direction, andsecond and third stator electrodes electrically isolated each other,arranged on the second inner surface and extending in the predetermineddirection; a first movable section arranged in the space to be movablein the predetermined direction, the first movable section includingfirst movable section electrodes facing the first stator electrodes,each of the first movable section electrodes extending in a directioncrossing the predetermined direction, and a second movable sectionelectrode extending in the predetermined direction to face the secondstator electrode; a second movable section arranged in the space to bemovable in the predetermined direction, and including third movablesection electrodes facing the first electrodes, each of the thirdmovable section electrodes extending in a direction crossing thepredetermined direction, and a fourth movable section electrodeextending in the predetermined direction to face the third statorelectrode, and a driving circuit configured to supply a first drivingsignal to the first stator electrodes, to supply one of a second drivingsignal and a first holding voltage signal to the second statorelectrode, and to supply one of a third driving signal and a secondholding voltage signal to the third stator electrode so as to move bothor one of the first and second movable sections in the predetermineddirection.
 9. The electrostatic actuator according to claim 8, furthercomprising first and second lenses arranged within the first and secondmovable sections, respectively.
 10. The electrostatic actuator accordingto claim 8, wherein the first movable section is capable of beingmoved-in the space in the predetermined direction with the fourthmovable section electrode being attracted to the third stator electrodeso as to hold the second movable section.
 11. The electrostatic actuatoraccording to claim 8, wherein the second and third stator electrodesextend substantially in parallel in the predetermined direction, and thesecond and fourth movable section electrodes also extend substantiallyin parallel in the predetermined direction.
 12. The electrostaticactuator according to claim 8, wherein the second and third statorelectrodes are planar electrodes extending in the predetermineddirection and arranged separately from each other in the predetermineddirection, and the first and second movable sections are moved withinthe range in which the second and third stator electrodes are extendedin the predetermined direction.
 13. An imaging apparatus for forming animage of a subject on an image-forming surface, comprising: first statorelectrodes arranged in a predetermined direction and extending in adirection crossing the predetermined direction; a second statorelectrode arranged to face the first stator electrodes and extending inthe predetermined direction; a third stator electrode arranged to facethe first stator electrodes and extending in the predetermined directionso as to be electrically isolated from the second stator electrode; afirst movable section having a first hollow space, provided with firstand second movable section electrodes, arranged movable within a movingspace in the predetermined direction, the moving space being definedbetween the first stator electrodes and the second stator electrode, thefirst movable section electrodes being mounted to the first movablesection to face the first stator electrodes, and the second movablesection electrode being mounted to the first movable section to face thesecond stator electrode; a second movable section having a second hollowspace, provided with third and fourth movable section electrodes,arranged independently of the first movable section, the second movablesection being movable within the moving space in the predetermineddirection, the third movable section electrodes being mounted to thesecond movable section to face the first stator electrodes, and thefourth movable section electrode being mounted to the second movablesection to face the third stator electrode; a first optical lens systemhaving a first optical axis arranged in the predetermined directionwithin the first hollow space; a second optical system having a secondoptical axis arranged in the predetermined direction within the secondhollow space, the image forming surface configured to face an image of asubject depending on the positions of the first and second lens systemsrelative to the image-forming surface; and a driving circuit configuredto supply a first driving signal to the first stator electrodes, tosupply one of a second driving signal and a first holding voltage signalto the second stator electrode, and to supply one of a third drivingsignal and a second holding voltage signal to the third stator electrodeso as to move both or one of the first and second movable sections inthe predetermined direction.
 14. The imaging apparatus according toclaim 13, wherein the second and third stator electrodes extendsubstantially in parallel in the predetermined direction, and the secondand fourth movable section electrodes also extend substantially inparallel in the predetermined direction.
 15. The imaging apparatusaccording to claim 13, wherein the second and third stator electrodesare planar electrodes extending in the predetermined direction andseparated from each other in the moving direction, and the first andsecond movable sections are moved within the ranges in which the secondand third stator electrodes expand in the moving direction.
 16. A methodof driving an electrostatic actuator, said electrostatic actuatorcomprising: first stator electrodes arranged in a predetermineddirection and extending in a direction crossing the predetermineddirection; a second stator electrode arranged to face the first statorelectrodes and extending in the predetermined direction; a third statorelectrode arranged to face the first stator electrodes and extending inthe predetermined direction so as to be electrically isolated from thesecond stator electrode; a first movable section provided with first andsecond movable section electrodes, arranged movable within a movingspace in the predetermined direction, the moving space being definedbetween the first stator electrodes and the second stator electrode, thefirst movable section electrodes being mounted to the first movablesection to face the first stator electrodes, and the second movablesection electrode being mounted to the first movable section to face thesecond stator electrode; and a second movable section provided withthird and fourth movable section electrodes, arranged independently ofthe first movable section, the second movable section being movablewithin the moving space in the predetermined direction, the thirdmovable section electrodes being mounted to the second movable sectionto face the first stator electrodes, and the fourth movable sectionelectrode being mounted to the second movable section to face the thirdstator electrode; said method comprising: supplying a first driving adriving signal to the first stator electrodes; supplying one of a seconddriving voltage and a first holding voltage signal to the second statorelectrode; and supplying one of a third driving signal and a secondholding voltage signal to the third stator electrode wherein both or oneof the first and second movable sections move in the predetermineddirection.